By default the PDPs validation is turned on.
The XACML schemas (policy and context) are delivered with the jar file under the classpath root.
But the schemas are not picked up.
I assume that the reason is a insufficient loading from classpath. Would mean that the classpath is only scanned for the local application but not within JAR files.
Hint: The Spring framework distinguishes those two cases with classpath:/... and classpath*:/...