Is "deliberate" body contact a foul of some kind?? What penalty do you pay for doing it?? Is allegedly "accidentally" hitting the other guy with your stick a foul?? Penalty?? [I'm not actually a "dirty" sportsman, but I always wanted to know the limits of what I was allowed to do on defense].
You can make as much body contact as you want
as long as it is within 5 yards of a loose ball or you are contacting someone who has the ball in their possession. Moving screens, checks, pushes, etc. away from the ball are illegal for obvious reasons.
You can hit someone with your stick
as much as you want as long as it is not excessively wild or violent (aka swinging at someone's knee caps for no reason) or you contact them in the head. Basically, as long as you are checking towards someone's stick you can go after them full steam ahead. That's why we wear pretty hardy arm pads and gloves... and we still end up with some really nasty bruises.
So yeah, it is an incredibly violent sport and basically anything goes with regards to checking... as long as you aren't just totally out of control or hitting someone in the head. It has to appear that you are making some sort of play on the ball not just trying to inflict pain.