Depends exactly how you do it.

All in all, if you know where he is it's much safer to let the cops handle it. So what if you do sort it out with a few of your "larger friends"? He's probably got larger friends too, and he knows where you live.

The legality depends entirely on the location of the stolen property and the method of recovery. It's not the actual reclaiming that is illegal. We are talking about this particular iPad, which we only know to be on the thief's person, in a house, or in a car. The likelihood of reclaiming it without breaking a serious law is very low.

Ask O.J.

If "recovering" requires forcing your way into someones house and threating or overpowering them, then most jurisdictions.

It's a crappy situation, but he has to weigh the value of his iPad against the cost of possibly being charged with trespassing, breaking and entering, or worse. He could end up with more severe charges against him than the thief.

If this is not a marketing stunt for an app, then he seems to be going about it the right way. The publicity will hopefully put pressure on the authorities to act.