diff --git a/app/models/category.rb b/app/models/category.rb
index fc9d1377570..6a0e0d5f338 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -933,6 +933,10 @@ class Category < ActiveRecord::Base
     end
   end
 
+  def has_restricted_tags?
+    tags.count > 0 || tag_groups.count > 0
+  end
+
   private
 
   def should_update_reviewables?
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 25c7e2678df..24645833a75 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -4810,6 +4810,12 @@ en:
         other: '"%{tag_name}" is restricted to the following categories: %{category_names}'
       synonym: 'Synonyms are not allowed. Use "%{tag_name}" instead.'
       has_synonyms: '"%{tag_name}" cannot be used because it has synonyms.'
+      restricted_tags_cannot_be_used_in_category:
+        one: 'The "%{tags}" tag cannot be used in the "%{category}" category. Please remove it.'
+        other: 'The following tags cannot be used in the "%{category}" category: %{tags}. Please remove them.'
+      category_does_not_allow_tags:
+        one: 'The "%{category}" category does not allow the "%{tags}" tag. Please remove it.'
+        other: 'The "%{category}" category does not allow the following tags: "%{tags}". Please remove them.'
     required_tags_from_group:
       one: "You must include at least %{count} %{tag_group_name} tag. The tags in this group are: %{tags}."
       other: "You must include at least %{count} %{tag_group_name} tags. The tags in this group are: %{tags}."
diff --git a/lib/discourse_tagging.rb b/lib/discourse_tagging.rb
index 4b2cb3db435..28fa7fe0592 100644
--- a/lib/discourse_tagging.rb
+++ b/lib/discourse_tagging.rb
@@ -175,6 +175,51 @@ module DiscourseTagging
     end
   end
 
+  def self.validate_category_restricted_tags(guardian, model, category, tags = [])
+    return true if tags.blank? || category.blank?
+
+    tags = tags.map(&:name) if Tag === tags[0]
+    tags_restricted_to_categories = Hash.new { |h, k| h[k] = Set.new }
+
+    query = Tag.where(name: tags)
+    query.joins(tag_groups: :categories).pluck(:name, 'categories.id').each do |(tag, cat_id)|
+      tags_restricted_to_categories[tag] << cat_id
+    end
+    query.joins(:categories).pluck(:name, 'categories.id').each do |(tag, cat_id)|
+      tags_restricted_to_categories[tag] << cat_id
+    end
+
+    unallowed_tags = tags_restricted_to_categories.keys.select do |tag|
+      !tags_restricted_to_categories[tag].include?(category.id)
+    end
+
+    if unallowed_tags.present?
+      msg = I18n.t(
+        "tags.forbidden.restricted_tags_cannot_be_used_in_category",
+        count: unallowed_tags.size,
+        tags: unallowed_tags.sort.join(", "),
+        category: category.name
+      )
+      model.errors.add(:base, msg)
+      return false
+    end
+
+    if !category.allow_global_tags && category.has_restricted_tags?
+      unrestricted_tags = tags - tags_restricted_to_categories.keys
+      if unrestricted_tags.present?
+        msg = I18n.t(
+          "tags.forbidden.category_does_not_allow_tags",
+          count: unrestricted_tags.size,
+          tags: unrestricted_tags.sort.join(", "),
+          category: category.name
+        )
+        model.errors.add(:base, msg)
+        return false
+      end
+    end
+    true
+  end
+
   TAG_GROUP_RESTRICTIONS_SQL ||= <<~SQL
     tag_group_restrictions AS (
       SELECT t.id as tag_id, tgm.id as tgm_id, tg.id as tag_group_id, tg.parent_tag_id as parent_tag_id,
diff --git a/lib/topic_creator.rb b/lib/topic_creator.rb
index 9119ec95511..c7e812f8160 100644
--- a/lib/topic_creator.rb
+++ b/lib/topic_creator.rb
@@ -30,9 +30,10 @@ class TopicCreator
       existing_tags = tags.present? ? Tag.where(name: tags) : []
       valid_tags = guardian.can_create_tag? ? tags : existing_tags
 
-      # both add to topic.errors
+      # all add to topic.errors
       DiscourseTagging.validate_min_required_tags_for_category(guardian, topic, category, valid_tags)
       DiscourseTagging.validate_required_tags_from_group(guardian, topic, category, existing_tags)
+      DiscourseTagging.validate_category_restricted_tags(guardian, topic, category, valid_tags)
     end
 
     DiscourseEvent.trigger(:after_validate_topic, topic, self)
diff --git a/spec/integration/category_tag_spec.rb b/spec/integration/category_tag_spec.rb
index 1f3fa9fbc24..6319f0e6393 100644
--- a/spec/integration/category_tag_spec.rb
+++ b/spec/integration/category_tag_spec.rb
@@ -31,11 +31,25 @@ describe "category tag restrictions" do
     end
 
     it "tags belonging to that category can only be used there" do
-      post = create_post(category: category_with_tags, tags: [tag1.name, tag2.name, tag3.name])
-      expect(post.topic.tags).to contain_exactly(tag1, tag2)
+      msg = I18n.t(
+        "tags.forbidden.category_does_not_allow_tags",
+        count: 1,
+        tags: tag3.name,
+        category: category_with_tags.name
+      )
+      expect {
+        create_post(category: category_with_tags, tags: [tag1.name, tag2.name, tag3.name])
+      }.to raise_error(StandardError, msg)
 
-      post = create_post(category: other_category, tags: [tag1.name, tag2.name, tag3.name])
-      expect(post.topic.tags).to contain_exactly(tag3)
+      msg = I18n.t(
+        "tags.forbidden.restricted_tags_cannot_be_used_in_category",
+        count: 2,
+        tags: [tag1, tag2].map(&:name).sort.join(", "),
+        category: other_category.name
+      )
+      expect {
+        create_post(category: other_category, tags: [tag1.name, tag2.name, tag3.name])
+      }.to raise_error(StandardError, msg)
     end
 
     it "search can show only permitted tags" do
@@ -55,10 +69,19 @@ describe "category tag restrictions" do
     end
 
     it "can't create new tags in a restricted category" do
-      post = create_post(category: category_with_tags, tags: [tag1.name, "newtag"])
-      expect_same_tag_names(post.topic.tags, [tag1])
-      post = create_post(category: category_with_tags, tags: [tag1.name, "newtag"], user: admin)
-      expect_same_tag_names(post.topic.tags, [tag1])
+      msg = I18n.t(
+        "tags.forbidden.category_does_not_allow_tags",
+        count: 1,
+        tags: "newtag",
+        category: category_with_tags.name
+      )
+      expect {
+        create_post(category: category_with_tags, tags: [tag1.name, "newtag"])
+      }.to raise_error(StandardError, msg)
+
+      expect {
+        create_post(category: category_with_tags, tags: [tag1.name, "newtag"], user: admin)
+      }.to raise_error(StandardError, msg)
     end
 
     it "can create new tags in a non-restricted category" do
@@ -149,8 +172,15 @@ describe "category tag restrictions" do
     end
 
     it "enforces restrictions when creating a topic" do
-      post = create_post(category: category, tags: [tag1.name, "newtag"])
-      expect(post.topic.tags.map(&:name)).to eq([tag1.name])
+      msg = I18n.t(
+        "tags.forbidden.category_does_not_allow_tags",
+        count: 1,
+        tags: "newtag",
+        category: category.name
+      )
+      expect {
+        create_post(category: category, tags: [tag1.name, "newtag"])
+      }.to raise_error(StandardError, msg)
     end
 
     it "handles colons" do
diff --git a/spec/lib/new_post_manager_spec.rb b/spec/lib/new_post_manager_spec.rb
index 5344e328d07..532a6f1008c 100644
--- a/spec/lib/new_post_manager_spec.rb
+++ b/spec/lib/new_post_manager_spec.rb
@@ -52,6 +52,53 @@ describe NewPostManager do
       expect(result.post).to be_a(Post)
     end
 
+    it "doesn't enqueue topic if it doesn't meet the tag restrictions of the category" do
+      tag1 = Fabricate(:tag)
+      tag2 = Fabricate(:tag)
+      tag3 = Fabricate(:tag)
+      tag_group = Fabricate(:tag_group, tags: [tag2])
+      category = Fabricate(:category, tags: [tag1], tag_groups: [tag_group])
+      category.custom_fields[Category::REQUIRE_TOPIC_APPROVAL] = true
+      category.save!
+
+      manager = NewPostManager.new(
+        user,
+        raw: 'this is a new post',
+        title: 'this is a new post',
+        category: category.id,
+        tags: [tag1.name, tag3.name]
+      )
+      result = manager.perform
+      expect(result.success?).to eq(false)
+      expect(result.reviewable.persisted?).to eq(false)
+      expect(result.errors.full_messages).to contain_exactly(
+        I18n.t(
+          "tags.forbidden.category_does_not_allow_tags",
+          count: 1,
+          category: category.name,
+          tags: tag3.name
+        )
+      )
+
+      manager = NewPostManager.new(
+        user,
+        raw: 'this is a new post',
+        title: 'this is a new post',
+        category: category.id,
+        tags: [tag2.name, tag3.name]
+      )
+      result = manager.perform
+      expect(result.success?).to eq(false)
+      expect(result.reviewable.persisted?).to eq(false)
+      expect(result.errors.full_messages).to contain_exactly(
+        I18n.t(
+          "tags.forbidden.category_does_not_allow_tags",
+          count: 1,
+          category: category.name,
+          tags: tag3.name
+        )
+      )
+    end
   end
 
   context "default handler" do
diff --git a/spec/lib/topic_creator_spec.rb b/spec/lib/topic_creator_spec.rb
index d311e23d350..c5bdf02f96f 100644
--- a/spec/lib/topic_creator_spec.rb
+++ b/spec/lib/topic_creator_spec.rb
@@ -84,6 +84,11 @@ describe TopicCreator do
     context 'tags' do
       fab!(:tag1) { Fabricate(:tag, name: "fun") }
       fab!(:tag2) { Fabricate(:tag, name: "fun2") }
+      fab!(:tag3) { Fabricate(:tag, name: "fun3") }
+      fab!(:tag4) { Fabricate(:tag, name: "fun4") }
+      fab!(:tag5) { Fabricate(:tag, name: "fun5") }
+      fab!(:tag_group1) { Fabricate(:tag_group, tags: [tag1]) }
+      fab!(:tag_group2) { Fabricate(:tag_group, tags: [tag2]) }
 
       before do
         SiteSetting.tagging_enabled = true
@@ -180,6 +185,203 @@ describe TopicCreator do
           ).to be_truthy
         end
       end
+
+      context "when category has restricted tags or tag groups" do
+        fab!(:category) { Fabricate(:category, tags: [tag3], tag_groups: [tag_group1]) }
+
+        it "allows topics without any tags" do
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic without tags",
+            raw: "hello this is a test topic without tags",
+            category: category.id,
+          )
+          expect(tc.valid?).to eq(true)
+          expect(tc.errors).to be_empty
+          topic = tc.create
+          expect(topic.tags).to be_empty
+        end
+
+        it "allows topics if they use tags only from the tags set that the category restricts" do
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags",
+            raw: "hello this is a test topic with tags",
+            category: category.id,
+            tags: [tag1.name, tag3.name]
+          )
+          expect(tc.valid?).to eq(true)
+          expect(tc.errors).to be_empty
+          topic = tc.create
+          expect(topic.tags).to contain_exactly(tag1, tag3)
+        end
+
+        it "allows topics to use tags that are restricted in multiple categories" do
+          category2 = Fabricate(:category, tags: [tag5], tag_groups: [tag_group1])
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags",
+            raw: "hello this is a test topic with tags",
+            category: category2.id,
+            tags: [tag1.name, tag5.name]
+          )
+          expect(tc.valid?).to eq(true)
+          expect(tc.errors).to be_empty
+          topic = tc.create
+          expect(topic.tags).to contain_exactly(tag1, tag5)
+
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags 1",
+            raw: "hello this is a test topic with tags",
+            category: category.id,
+            tags: [tag1.name, tag3.name]
+          )
+          expect(tc.valid?).to eq(true)
+          expect(tc.errors).to be_empty
+          topic = tc.create
+          expect(topic.tags).to contain_exactly(tag1, tag3)
+
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags 2",
+            raw: "hello this is a test topic with tags",
+            category: category.id,
+            tags: [tag1.name, tag5.name]
+          )
+          expect(tc.valid?).to eq(false)
+          expect(tc.errors.full_messages).to contain_exactly(
+            I18n.t(
+              "tags.forbidden.restricted_tags_cannot_be_used_in_category",
+              count: 1,
+              tags: tag5.name,
+              category: category.name
+            )
+          )
+        end
+
+        it "rejects topics if they use a tag outside the set of tags that the category restricts" do
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags",
+            raw: "hello this is a test topic with tags",
+            category: category.id,
+            tags: [tag2.name, tag1.name]
+          )
+          expect(tc.valid?).to eq(false)
+          expect(tc.errors.full_messages).to contain_exactly(
+            I18n.t(
+              "tags.forbidden.category_does_not_allow_tags",
+              count: 1,
+              tags: tag2.name,
+              category: category.name
+            )
+          )
+
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags",
+            raw: "hello this is a test topic with tags",
+            category: category.id,
+            tags: [tag2.name, tag5.name, tag3.name]
+          )
+          expect(tc.valid?).to eq(false)
+          expect(tc.errors.full_messages).to contain_exactly(
+            I18n.t(
+              "tags.forbidden.category_does_not_allow_tags",
+              count: 2,
+              tags: [tag2, tag5].map(&:name).sort.join(", "),
+              category: category.name
+            )
+          )
+        end
+
+        it "rejects topics in other categories if a restricted tag of a category are used" do
+          category2 = Fabricate(:category)
+          tc = TopicCreator.new(
+            user,
+            Guardian.new(user),
+            title: "hello this is a test topic with tags",
+            raw: "hello this is a test topic with tags",
+            category: category2.id,
+            tags: [tag1.name, tag2.name]
+          )
+          expect(tc.valid?).to eq(false)
+          expect(tc.errors.full_messages).to contain_exactly(
+            I18n.t(
+              "tags.forbidden.restricted_tags_cannot_be_used_in_category",
+              count: 1,
+              tags: tag1.name,
+              category: category2.name
+            )
+          )
+        end
+
+        context "and allows other tags" do
+          before { category.update!(allow_global_tags: true) }
+
+          it "allows topics to use tags that aren't restricted by any category" do
+            tc = TopicCreator.new(
+              user,
+              Guardian.new(user),
+              title: "hello this is a test topic with tags",
+              raw: "hello this is a test topic with tags",
+              category: category.id,
+              tags: [tag1.name, tag2.name, tag3.name, tag5.name]
+            )
+            expect(tc.valid?).to eq(true)
+            expect(tc.errors).to be_empty
+            topic = tc.create
+            expect(topic.tags).to contain_exactly(tag1, tag2, tag3, tag5)
+          end
+
+          it "rejects topics if they use restricted tags of another category" do
+            Fabricate(:category, tags: [tag5], tag_groups: [tag_group2])
+            tc = TopicCreator.new(
+              user,
+              Guardian.new(user),
+              title: "hello this is a test topic with tags",
+              raw: "hello this is a test topic with tags",
+              category: category.id,
+              tags: [tag1.name, tag5.name]
+            )
+            expect(tc.valid?).to eq(false)
+            expect(tc.errors.full_messages).to contain_exactly(
+              I18n.t(
+                "tags.forbidden.restricted_tags_cannot_be_used_in_category",
+                count: 1,
+                tags: tag5.name,
+                category: category.name
+              )
+            )
+
+            tc = TopicCreator.new(
+              user,
+              Guardian.new(user),
+              title: "hello this is a test topic with tags",
+              raw: "hello this is a test topic with tags",
+              category: category.id,
+              tags: [tag1.name, tag2.name, tag5.name]
+            )
+            expect(tc.valid?).to eq(false)
+            expect(tc.errors.full_messages).to contain_exactly(
+              I18n.t(
+                "tags.forbidden.restricted_tags_cannot_be_used_in_category",
+                count: 2,
+                tags: [tag2, tag5].map(&:name).sort.join(", "),
+                category: category.name
+              )
+            )
+          end
+        end
+      end
     end
 
     context 'personal message' do