Well I think Obama himself once suggested a moat filled with alligators.
Quite frankly I think common sense would do the trick.
A young colleague of mine spent a semester of college in Denmark.
His student visa assigned him a unique ID number (similar to an SSN) that would be required of him to do ANYTHING in Denmark. To do any banking, rent an apartment, buy a bus pass, check out a library book, etc.
His visa came with a very stern warning that he must be out of the country by June 30, 20XX. And that the ID number he had been assigned would turn into a pumpkin on that date.
Some countries, it seems, take this seriously.
I would prefer sharks with frickin' laser beams attached to their heads.
Close. Obomba accused REPUBLICANS of wanting a moat filled with alligators.
Actually, in a way he was right. That's not a bad idea.