Poker rules

I'm curious about a situation I've come across several times in live NL hold em tournament play. Say the blinds are 500 and 1000 and I am playing from past the blinds. Now, I raise to 2000 and I get several callers. Then action comes back to the big blind. He goes all in for 2100.

Say I have AA and I want to go all in here? Am I allowed?

I think I am because the big blind just raised me. By going all in, he raised me by 100.

I've heard people say I'm not allowed to do this because technically I wasn't raised. They say, the big blind would have to double my raise in order to raise me. Since they didn't have enough chips to double my raise, them going all in is technically not a raise and therefore, I cannot reraise.

I agree that he would have to double my raise to make a raise, unless he doesn't have enough, then he can raise by going all in. So, by going all in, he raises me 100. Therefore, I have to put another 100 chips in the pot, which is a raise to me and I can reraise if I want to. It just makes sense to me, but I've had the other argument raised against me several times. Does anyone know about this technicality, or where I can find an explanation of the official rules for this situation to print out and take to my game?

In no-limit the raise must be at least the size of the previous raise in order to reopen the betting. You can only complete the 100 in this situation.

In LIMIT holdem a raise of half the bet is sufficient to reopen the betting.

ahh.. ok... I didn't know that. Thanks for the info.

I recommend this rule book.