diff --git a/src/policy/block/minerfund.h b/src/policy/block/minerfund.h
--- a/src/policy/block/minerfund.h
+++ b/src/policy/block/minerfund.h
@@ -29,7 +29,7 @@
         : m_block(block), m_blockReward(blockReward),
           m_consensusParams(consensusParams), m_blockIndex(blockIndex) {}
 
-    bool operator()() override;
+    bool operator()(BlockPolicyValidationState &state) override;
 };
 
 #endif // BITCOIN_POLICY_BLOCK_MINERFUND_H
diff --git a/src/policy/block/minerfund.cpp b/src/policy/block/minerfund.cpp
--- a/src/policy/block/minerfund.cpp
+++ b/src/policy/block/minerfund.cpp
@@ -8,7 +8,7 @@
 #include <consensus/activation.h>
 #include <minerfund.h>
 
-bool MinerFundPolicy::operator()() {
+bool MinerFundPolicy::operator()(BlockPolicyValidationState &state) {
     if (!m_blockIndex.pprev ||
         !IsWellingtonEnabled(m_consensusParams, m_blockIndex.pprev)) {
         // Do not apply the miner fund policy before Wellington activates.
@@ -16,6 +16,12 @@
     }
 
     assert(m_block.vtx.size());
-    return CheckMinerFund(m_consensusParams, m_blockIndex.pprev,
-                          m_block.vtx[0]->vout, m_blockReward);
+    bool validMinerFund = CheckMinerFund(m_consensusParams, m_blockIndex.pprev,
+                                         m_block.vtx[0]->vout, m_blockReward);
+
+    if (!validMinerFund) {
+        return state.Invalid(BlockPolicyValidationResult::POLICY_VIOLATION,
+                             "policy-bad-miner-fund");
+    }
+    return true;
 }
diff --git a/src/policy/block/parkingpolicy.h b/src/policy/block/parkingpolicy.h
--- a/src/policy/block/parkingpolicy.h
+++ b/src/policy/block/parkingpolicy.h
@@ -5,11 +5,26 @@
 #ifndef BITCOIN_POLICY_BLOCK_PARKINGPOLICY_H
 #define BITCOIN_POLICY_BLOCK_PARKINGPOLICY_H
 
+#include <consensus/validation.h> // For ValidationState<>
+
+/**
+ * A "reason" why a block did not pass block policy checks.
+ */
+enum class BlockPolicyValidationResult {
+    //! Initial value. Policy rule has not yet been violated.
+    POLICY_RESULT_UNSET = 0,
+    //! A block policy rule was violated. This block should be parked.
+    POLICY_VIOLATION,
+};
+
+class BlockPolicyValidationState
+    : public ValidationState<BlockPolicyValidationResult> {};
+
 struct ParkingPolicy {
     virtual ~ParkingPolicy() {}
 
     // Return true if a policy succeeds. False will park the block.
-    virtual bool operator()() = 0;
+    virtual bool operator()(BlockPolicyValidationState &state) = 0;
 };
 
 #endif // BITCOIN_POLICY_BLOCK_PARKINGPOLICY_H
diff --git a/src/test/policy_block_tests.cpp b/src/test/policy_block_tests.cpp
--- a/src/test/policy_block_tests.cpp
+++ b/src/test/policy_block_tests.cpp
@@ -72,14 +72,22 @@
             CBlock block = BlockWithoutMinerFund(blockReward);
             MinerFundPolicy check(consensusParams, blockIndex, block,
                                   blockReward);
-            BOOST_CHECK(check());
+
+            BlockPolicyValidationState state;
+            BOOST_CHECK(check(state));
+            BOOST_CHECK(!state.IsInvalid());
         }
     };
 
     auto checkMinerFundPolicy = [&](CBlock block, bool expected) {
+        BlockPolicyValidationState state;
         BOOST_CHECK_EQUAL(MinerFundPolicy(consensusParams, lastBlockIndexRef,
-                                          block, blockReward)(),
+                                          block, blockReward)(state),
                           expected);
+        BOOST_CHECK_EQUAL(state.IsInvalid(), !expected);
+        if (!expected) {
+            BOOST_CHECK_EQUAL(state.GetRejectReason(), "policy-bad-miner-fund");
+        }
     };
 
     const std::vector<Amount> minerFundsTooSmall = {1 * SATOSHI, minerFund / 2,
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2728,9 +2728,17 @@
                 consensusParams, *pindexNew, blockConnecting, blockReward));
 
             if (!std::all_of(parkingPolicies.begin(), parkingPolicies.end(),
-                             [&](const auto &policy) { return (*policy)(); })) {
-                LogPrintf("Park block %s because it violated a block policy\n",
-                          blockhash.ToString());
+                             [&](const auto &policy) {
+                                 BlockPolicyValidationState blockPolicyState;
+                                 bool ret = (*policy)(blockPolicyState);
+                                 if (!ret) {
+                                     LogPrintf("Park block %s because it "
+                                               "violated a block policy: %s\n",
+                                               blockhash.ToString(),
+                                               blockPolicyState.ToString());
+                                 }
+                                 return ret;
+                             })) {
                 pindexNew->nStatus = pindexNew->nStatus.withParked();
                 m_blockman.m_dirty_blockindex.insert(pindexNew);
                 return false;
diff --git a/test/functional/abc_feature_minerfund.py b/test/functional/abc_feature_minerfund.py
--- a/test/functional/abc_feature_minerfund.py
+++ b/test/functional/abc_feature_minerfund.py
@@ -153,7 +153,9 @@
                     assert tip["status"] != "active"
                     return tip["status"] == "parked"
             return False
-        self.wait_until(lambda: parked_block(first_block_no_miner_fund))
+
+        with node.assert_debug_log(expected_msgs=['policy-bad-miner-fund']):
+            self.wait_until(lambda: parked_block(first_block_no_miner_fund))
 
         # Unpark the block
         node.unparkblock(first_block_no_miner_fund)