Witnessed a F-5 Tiger intercepting an Cessna 172 in a temporary active CTR in Switzerland (military airport). The Cessna wasn't on the frequency, so the TWR couldn't contact him.
Outcome? Think the F5-Pilot had loads of fun (although he had to deploy full flaps and gear) but registered the a/c's immatriculation. As far as I know they tracked it back and it ended up in a fine for the cessna-pilot