Why you so cute.
Take down his Identification Card and copy the details.
If he say he doesn't have his IC with him, call police (He'll
somehow make one IC out)
Or get him to dial his house number or closest kin to verify/get
his particulars.
Many ways to deal. Got to think harder.
Ask him if he wants to go to lock up or let you copy down his
particulars.
When you have his particulars and regconise him. There is nothing
much he can do except to look for another victim, unless he's a
hardcore offender. Which i'd doubt.
If anything problem arises again, you can threaten to hand over his
particulars to the police.
Cheers