Bets between friends -- Prop/Sports/Anything -- Legality?

[Mizzmazz]

Hi,

I've been curious lately about the law (U.S.)and how it applies to bets between friends or acquaintances.

Let's say I want to bet my buddy in private on an NFL game or a UFC mixed martial arts fight -- legally is this allowed?

Let's take it further.. if there was a 50-person fantasy football league with $200/head and some government agency or the police department got wind of it -- would it be legal or is this considered a layman's version of bookmaking and therefore illegal?

I'm not thinking of starting anything like this I was just always curious if it's okay to make bets between friends in private. I see people on these forums and other devices openly wagering on HU matches (see HSNL forum for instance) without hesitation.

Are there federal laws that apply to this or would it be state-based... or is it completely allowed unless you are some sort of organization?

Thanks

Mizzmazz