hahah, i would just make up a random reason not to go if i was you.....
it would be pretty awkard to go to a party full of cops... what ever you do just make sure any weed aint on you
1.when your smoking a blunt and all of a sudden zone out a few minutes and forget it still in your hands
2.when you check the door 5-6 times to make sure you locked it
3.when you go to the kitchen to get SOME chips and end up eating 2 bags
4.when someone talking to you and you cant understand shit