diff --git a/backend/routers/caliper.py b/backend/routers/caliper.py
index 6b0e1c2..3c53e52 100644
--- a/backend/routers/caliper.py
+++ b/backend/routers/caliper.py
@@ -7,7 +7,7 @@ import uuid
 import logging
 from typing import Optional
 
-from fastapi import APIRouter, Header, Depends
+from fastapi import APIRouter, Header, Depends, HTTPException
 
 from db import get_db, get_cursor, r2d
 from auth import require_auth, check_feature_access, increment_feature_usage
@@ -35,15 +35,20 @@ def upsert_caliper(e: CaliperEntry, x_profile_id: Optional[str]=Header(default=N
     """Create or update caliper entry (upsert by date)."""
     pid = get_pid(x_profile_id)
 
-    # Phase 2: Check feature access (non-blocking, log only)
+    # Phase 4: Check feature access and ENFORCE
     access = check_feature_access(pid, 'caliper_entries')
     log_feature_usage(pid, 'caliper_entries', access, 'create')
 
     if not access['allowed']:
         logger.warning(
-            f"[FEATURE-LIMIT] User {pid} would be blocked: "
+            f"[FEATURE-LIMIT] User {pid} blocked: "
             f"caliper_entries {access['reason']} (used: {access['used']}, limit: {access['limit']})"
         )
+        raise HTTPException(
+            status_code=403,
+            detail=f"Limit erreicht: Du hast das Kontingent für Caliper-Einträge überschritten ({access['used']}/{access['limit']}). "
+                   f"Bitte kontaktiere den Admin oder warte bis zum nächsten Reset."
+        )
 
     with get_db() as conn:
         cur = get_cursor(conn)
diff --git a/backend/routers/circumference.py b/backend/routers/circumference.py
index bca2a14..41c06fa 100644
--- a/backend/routers/circumference.py
+++ b/backend/routers/circumference.py
@@ -7,7 +7,7 @@ import uuid
 import logging
 from typing import Optional
 
-from fastapi import APIRouter, Header, Depends
+from fastapi import APIRouter, Header, Depends, HTTPException
 
 from db import get_db, get_cursor, r2d
 from auth import require_auth, check_feature_access, increment_feature_usage
@@ -35,15 +35,20 @@ def upsert_circ(e: CircumferenceEntry, x_profile_id: Optional[str]=Header(defaul
     """Create or update circumference entry (upsert by date)."""
     pid = get_pid(x_profile_id)
 
-    # Phase 2: Check feature access (non-blocking, log only)
+    # Phase 4: Check feature access and ENFORCE
     access = check_feature_access(pid, 'circumference_entries')
     log_feature_usage(pid, 'circumference_entries', access, 'create')
 
     if not access['allowed']:
         logger.warning(
-            f"[FEATURE-LIMIT] User {pid} would be blocked: "
+            f"[FEATURE-LIMIT] User {pid} blocked: "
             f"circumference_entries {access['reason']} (used: {access['used']}, limit: {access['limit']})"
         )
+        raise HTTPException(
+            status_code=403,
+            detail=f"Limit erreicht: Du hast das Kontingent für Umfangs-Einträge überschritten ({access['used']}/{access['limit']}). "
+                   f"Bitte kontaktiere den Admin oder warte bis zum nächsten Reset."
+        )
 
     with get_db() as conn:
         cur = get_cursor(conn)
diff --git a/backend/routers/weight.py b/backend/routers/weight.py
index 414bd8b..2d49baa 100644
--- a/backend/routers/weight.py
+++ b/backend/routers/weight.py
@@ -7,7 +7,7 @@ import uuid
 import logging
 from typing import Optional
 
-from fastapi import APIRouter, Header, Depends
+from fastapi import APIRouter, Header, Depends, HTTPException
 
 from db import get_db, get_cursor, r2d
 from auth import require_auth, check_feature_access, increment_feature_usage
@@ -35,19 +35,23 @@ def upsert_weight(e: WeightEntry, x_profile_id: Optional[str]=Header(default=Non
     """Create or update weight entry (upsert by date)."""
     pid = get_pid(x_profile_id)
 
-    # Phase 2: Check feature access (non-blocking, log only)
+    # Phase 4: Check feature access and ENFORCE
     access = check_feature_access(pid, 'weight_entries')
 
     # Structured logging (always)
     log_feature_usage(pid, 'weight_entries', access, 'create')
 
-    # Warning if limit exceeded (legacy)
+    # BLOCK if limit exceeded
     if not access['allowed']:
         logger.warning(
-            f"[FEATURE-LIMIT] User {pid} would be blocked: "
+            f"[FEATURE-LIMIT] User {pid} blocked: "
             f"weight_entries {access['reason']} (used: {access['used']}, limit: {access['limit']})"
         )
-        # NOTE: Phase 2 does NOT block - just logs!
+        raise HTTPException(
+            status_code=403,
+            detail=f"Limit erreicht: Du hast das Kontingent für Gewichtseinträge überschritten ({access['used']}/{access['limit']}). "
+                   f"Bitte kontaktiere den Admin oder warte bis zum nächsten Reset."
+        )
 
     with get_db() as conn:
         cur = get_cursor(conn)