diff --git a/src/main/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslator.java b/src/main/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslator.java
index 8e61857..f7ff9b0 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslator.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslator.java
@@ -15,6 +15,8 @@
 package com.googlesource.gerrit.plugins.simplesubmitrules.config;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.data.LabelFunction;
 import com.google.gerrit.common.data.LabelType;
@@ -30,10 +32,9 @@
 import com.googlesource.gerrit.plugins.simplesubmitrules.api.CommentsRules;
 import com.googlesource.gerrit.plugins.simplesubmitrules.api.LabelDefinition;
 import com.googlesource.gerrit.plugins.simplesubmitrules.api.SubmitConfig;
-import java.util.Collection;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 /** Codec class used to convert {@link SubmitConfig} from/to a Gerrit config */
 @Singleton
@@ -73,9 +74,12 @@
   }
 
   static void applyCopyScoreRulesTo(
-      @Nullable Collection<String> copyScoreRules, LabelType labelType) {
-    if (copyScoreRules == null) {
-      return;
+      Set<String> copyScoreRules, Set<String> disallowedCopyScoreRules, LabelType labelType)
+      throws BadRequestException {
+    Set<String> disallowed =
+        Sets.intersection(ImmutableSet.copyOf(copyScoreRules), disallowedCopyScoreRules);
+    if (!disallowed.isEmpty()) {
+      throw new BadRequestException("copy score rules " + disallowed + " are forbidden");
     }
 
     labelType.setCopyMinScore(copyScoreRules.contains(ProjectConfig.KEY_COPY_MIN_SCORE));
@@ -153,8 +157,8 @@
       }
 
       if (definition.getFunction().isPresent()) {
-        List<String> disallowedLabelFunctions =
-            ImmutableList.copyOf(
+        Set<String> disallowedLabelFunctions =
+            ImmutableSet.copyOf(
                 hostPluginConfig.getStringList("disallowedLabelFunctions-" + label));
         LabelFunction function = definition.getFunction().get();
         if (disallowedLabelFunctions.contains(function.getFunctionName())) {
@@ -162,10 +166,16 @@
         }
         labelType.setFunction(function);
       }
+
       // TODO(hiesel): Remove fallback to copyScores
-      applyCopyScoreRulesTo(
-          definition.copyScoreRules != null ? definition.copyScoreRules : definition.copyScores,
-          labelType);
+      Set<String> copyScoreRules =
+          definition.copyScoreRules != null ? definition.copyScoreRules : definition.copyScores;
+      if (copyScoreRules != null) {
+        Set<String> disallowedCopyScoreRules =
+            ImmutableSet.copyOf(
+                hostPluginConfig.getStringList("disallowedCopyScoreRules-" + label));
+        applyCopyScoreRulesTo(copyScoreRules, disallowedCopyScoreRules, labelType);
+      }
     }
   }
 
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index 8ad2fa1..3da2fae 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -5,7 +5,7 @@
 - Ability to prevent submission if there are unresolved comments.
 - Ability to require approval, and to consider approval from the uploader of the
   latest patch set or not.
-- (soon!) a simple PolyGerrit UI to configure the labels and how they work.
+- A simple PolyGerrit UI to configure the labels and how they work.
 
 ### Inheritance
 This plugin supports configuration inheritance, following a worst case scenario when this is
@@ -124,3 +124,15 @@
 [plugin "simple-submit"]
   disallowedLabelFunctions-Code-Review = MaxNoBlock
 ```
+
+#### disallowedCopyScoreRules-<label-name>
+
+This config will prevent users from changing adding referenced copy score rules
+in the label configuration that is referenced in the name to a matching value.
+However, the config does not effect existing labels that already have
+the forbidden value.
+
+```
+[plugin "simple-submit"]
+  disallowedCopyScoreRules-Code-Review = copyMaxScore
+```
diff --git a/src/test/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslatorTest.java b/src/test/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslatorTest.java
index 4b3d61c..07799ad 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslatorTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/simplesubmitrules/config/ConfigTranslatorTest.java
@@ -16,17 +16,21 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.common.data.LabelType;
+import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.googlesource.gerrit.plugins.simplesubmitrules.api.LabelDefinition;
 import java.util.function.BiConsumer;
 import java.util.function.Predicate;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 public class ConfigTranslatorTest {
-  /** Test the translations for each config key */
+  @Rule public ExpectedException exception = ExpectedException.none();
+
   @Test
-  public void checkLabelTranslation() {
+  public void checkLabelTranslation() throws Exception {
     checkTranslation("copyMinScore", LabelType::isCopyMinScore, LabelType::setCopyMinScore);
     checkTranslation("copyMaxScore", LabelType::isCopyMaxScore, LabelType::setCopyMaxScore);
 
@@ -51,11 +55,22 @@
         LabelType::setCopyAllScoresOnTrivialRebase);
   }
 
+  @Test
+  public void checkDisallowedCopyScoreThrowsBadRequest() throws Exception {
+    exception.expect(BadRequestException.class);
+    exception.expectMessage("copy score rules [copyAllScoresIfNoChange] are forbidden");
+    ConfigTranslator.applyCopyScoreRulesTo(
+        ImmutableSet.of("copyAllScoresIfNoChange", "copyAllScoresOnMergeFirstParentUpdate"),
+        ImmutableSet.of("copyAllScoresIfNoChange"),
+        LabelType.withDefaultValues("Verified"));
+  }
+
   /** Helper method to check that conversion from/to Gerrit works for both true and false values */
   private static void checkTranslation(
       String copyScoreName,
       Predicate<LabelType> functionToCheck,
-      BiConsumer<LabelType, Boolean> functionToSet) {
+      BiConsumer<LabelType, Boolean> functionToSet)
+      throws Exception {
     checkLabelToGerritPresent(copyScoreName, functionToCheck);
     checkLabelToGerritAbsent(copyScoreName, functionToCheck);
 
@@ -92,18 +107,19 @@
   }
 
   private static void checkLabelToGerritPresent(
-      String copyScoreName, Predicate<LabelType> functionToCheck) {
+      String copyScoreName, Predicate<LabelType> functionToCheck) throws Exception {
     LabelType label = LabelType.withDefaultValues("Verified");
 
-    ConfigTranslator.applyCopyScoreRulesTo(ImmutableList.of(copyScoreName), label);
+    ConfigTranslator.applyCopyScoreRulesTo(
+        ImmutableSet.of(copyScoreName), ImmutableSet.of(), label);
     assertThat(functionToCheck.test(label)).named("[case %s:true]", copyScoreName).isTrue();
   }
 
   private static void checkLabelToGerritAbsent(
-      String copyScoreName, Predicate<LabelType> functionToCheck) {
+      String copyScoreName, Predicate<LabelType> functionToCheck) throws Exception {
     LabelType label = LabelType.withDefaultValues("Verified");
 
-    ConfigTranslator.applyCopyScoreRulesTo(ImmutableList.of(), label);
+    ConfigTranslator.applyCopyScoreRulesTo(ImmutableSet.of(), ImmutableSet.of(), label);
     assertThat(functionToCheck.test(label)).named("[case %s:false]", copyScoreName).isFalse();
   }
 }