i think you can get dq'd by taking someone out, but "rubbin' is racin'"
There are very few rules.
At the moment the Mark Room Rule (16) states that in an equipment overlap situation the Racer closest to the Mark must given enough room to safely round the mark by the racer farther away from the mark.
During slalom there is direct umpiring. A judge is on a Jetski watching the marks. If there is any dangerous or unfair Sailing then it is up to him/her to decide to DSQ the offending rider. Touching kites happens a lot in Slalom and does not necessarily mean that there is an infringement.