Thought so
Knows all his "rights" I have no doubt.
You could try asking him if he has a current visa and a work permit.
In my experience they often don't and turn out to be "over stayers".
The Immigration Service lifted 17 of our staff one night shift. Ah the good old days
To deal with those who were big on their rights I used to send one of my supervisors. Big Lad, West Indian with an impenetrable accent. Worked like a charm and they didn't dare complain about him 'cos he was Bl**k.