I'm going to agree with Ran that the law is the law. Everyone that smokes know that they are breaking the law and should be willing to accept the consequences if they are caught. Do I necessarily agree with the law, no. Do I think anonymously phoning in info about a party is a rather douchetastic thing to do, yes. Regardless though, they could have easily chosen not to break it.
The law is the law, no matter how much it sucks, and breaking it out of defiance on a small scale isn't going to change anything.
And before anyone jumps on my case, read my previous posts. I think cannabis should be legal.