diff --git a/src/java/org/apache/cassandra/db/guardrails/CMSSizeGuardrail.java b/src/java/org/apache/cassandra/db/guardrails/CMSSizeGuardrail.java
new file mode 100644
index 0000000000..e1fb4c0b9a
--- /dev/null
+++ b/src/java/org/apache/cassandra/db/guardrails/CMSSizeGuardrail.java
@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.cassandra.db.guardrails;
+
+import java.util.function.ToLongFunction;
+
+import org.apache.cassandra.service.ClientState;
+
+import static java.lang.String.format;
+
+public class CMSSizeGuardrail extends MinThreshold
+{
+    /**
+     * Creates a new minimum threshold guardrail.
+     *
+     * @param failThreshold   a {@link ClientState}-based provider of the value above which the operation should be aborted.
+     */
+    public CMSSizeGuardrail(ToLongFunction<ClientState> failThreshold)
+    {
+        super("minimum_cms_size",
+              null,
+              state -> -1,
+              failThreshold,
+              (isWarning, what, value, threshold) ->
+              format("The CMS size of %s is below the failure threshold of %s. " +
+                     "Reconfigure CMS so its total size (sum of replication factors across all datacenters) is at least %s.",
+                     value, threshold, threshold));
+        this.throwOnNullClientState = true;
+    }
+
+    public void guard(int totalNodes, int cmsSize)
+    {
+        // A cluster can't host more CMS replicas than it has nodes. If the request already uses every node there's
+        // nothing more to enforce (e.g. during bootstrap), and requiring more would brick reconfiguration. Otherwise
+        // the request must meet the configured minimum, even when the threshold exceeds the current cluster size, so
+        // an operator can't sidestep the floor by setting a high threshold. An operator who genuinely wants a smaller
+        // CMS should disable the guardrail. When it is disabled, guard() below is a no-op.
+        if (cmsSize >= totalNodes)
+            return;
+
+        guard(cmsSize, "CMS", false, null);
+    }
+}
diff --git a/src/java/org/apache/cassandra/db/guardrails/Guardrails.java b/src/java/org/apache/cassandra/db/guardrails/Guardrails.java
index aa0018d827..cc44b5add8 100644
--- a/src/java/org/apache/cassandra/db/guardrails/Guardrails.java
+++ b/src/java/org/apache/cassandra/db/guardrails/Guardrails.java
@@ -618,17 +618,7 @@ public final class Guardrails implements GuardrailsMBean
     /**
      * Guardrail on the minimum CMS size (aggregate replication factor across DCs).
      */
-    public static final MinThreshold minimumCmsSize =
-    (MinThreshold) new MinThreshold("minimum_cms_size",
-                     null,
-                     state -> -1,
-                     state -> CONFIG_PROVIDER.getOrCreate(state).getMinimumCmsSizeFailThreshold(),
-                     (isWarning, what, value, threshold) ->
-                     format("The CMS size of %s is below the failure threshold of %s. " +
-                            "Reconfigure CMS so its total size (sum of replication factors across all datacenters) is at least %s.",
-                            value, threshold, threshold))
-                     // CMS reconfiguration is a system operation with no ClientState; make it abort rather than just log.
-                     .throwOnNullClientState(true);
+    public static final CMSSizeGuardrail minimumCmsSize = new CMSSizeGuardrail(state -> CONFIG_PROVIDER.getOrCreate(state).getMinimumCmsSizeFailThreshold());
 
     /**
      * Guardrail on the maximum replication factor.
diff --git a/src/java/org/apache/cassandra/tcm/CMSOperations.java b/src/java/org/apache/cassandra/tcm/CMSOperations.java
index 089ca93c7f..615f1e9034 100644
--- a/src/java/org/apache/cassandra/tcm/CMSOperations.java
+++ b/src/java/org/apache/cassandra/tcm/CMSOperations.java
@@ -188,15 +188,7 @@ public class CMSOperations implements CMSOperationsMBean
         int cmsSize = params.options.values().stream()
                                     .mapToInt(Integer::parseInt)
                                     .sum();
-        // A cluster can't host more CMS replicas than it has nodes. If the request already uses every node there's
-        // nothing more to enforce (e.g. during bootstrap), and requiring more would brick reconfiguration. Otherwise
-        // the request must meet the configured minimum, even when the threshold exceeds the current cluster size, so
-        // an operator can't sidestep the floor by setting a high threshold. An operator who genuinely wants a smaller
-        // CMS should disable the guardrail. When it is disabled, guard() below is a no-op.
-        if (cmsSize >= totalNodes)
-            return;
-
-        Guardrails.minimumCmsSize.guard(cmsSize, "CMS", false, null);
+        Guardrails.minimumCmsSize.guard(totalNodes, cmsSize);
     }
 
     @Override