The assumption on Intel is that there are no barriers once you're in the ME. You can't defend against a hostile ME. The security model is already violated. Mayb

The assumption on Intel is that there are no barriers once you're in the ME. You can't defend against a hostile ME. The security model is already violated. Maybe there should be a barrier between the ME and the CPU, but as can be seen here Intel feel that the ME should be in a position to put the CPU in debug mode so shrug.