My understanding is that the rules prohibit:Are they drop kicking the guy with the ball?
- hitting other players in the head or neck
- punching, headbutting, and elbowing from behind
- kicking other players
- tackling other players using straight arms or legs
- blocking an opponent so another teammate can hit him
- hitting players on the ground (the rules also explicitly forbid jumping on players on the ground, so I guess there is some latitude on what constitute 'hitting')
Some of this restrictions are relaxed during open fighting which is allowed only on a 1-to-1 basis, and only if both players involved have manifested their intention to fight.