When is it okay to punch a kid in the face?

Is it ever acceptable to clench your fist, cock your arm back, and smash a kid right in the jaw? No? What if he's 17, taller than you, and he just stole an old lady's purse then knocked her to the ground? See, I knew I could convince you.

There are plenty of scenarios that could fall into this gray area. Just think of some crazy shit - like a teenage serial killer who took your family hostage. You might be ethically justified in teaching him a lesson.

Hmmm... Is that even legal though? Let's say you see your daughter's 16-year-old asshole boyfriend punch her in the jaw like that dude who socked Snooki. Could you get arrested for punching him back? What if you catch a teenager trying to steal your wallet? Could you face jail time for giving him a black eye?

The thought came to me recently on the way home from work. Center City Philly. It's dark out and I'm walking through a sketchy part of town. I see a group of questionable teenagers roughhousing on in the street. I thought - what if these kids decide to start fucking with me? A lone white guy quietly walking through their neighborhood with no other adults in sight. Truth is, they'd destroy me in a fight. But I could probably manage to land a couple of jabs.

So in that scenario - what happens legally? A group of 15 and 16-year-old boys. A couple of them with black eyes, maybe even one with a broken nose. Then a 34-year-old yuppie beaten to a pulp. Would I face charges?

Okay, that's enough setup. Most of you probably agree there are instances where a kid might deserve an uppercut to the jaw. Now that I've roped you in - consider these situations:

• You're on the bus and you see a kid call an old lady a bitch.
• Two kids walk up to you yelling racial slurs then start pushing you, trying to start something.
• You walk outside late at night and catch a kid reaching the broken glass of your car's window, trying to steal your shit.
• You're walking on the sidewalk, when a car full of teenagers drive by slowly and throw a bag of shit at your face - then they are forced to stop half a block ahead because of traffic.

Punch or no punch? And what's the age limit? For any of the scenarios above? Maybe it's easy to say you'd knock out a 17-year-old thug. But what if he's 16, 15... 14?