I think it really is about local mindset. Possesion is still a felony in some areas.
I am sure it was there. Not that it is right, but the police have the right to investigate a felony. As far as some of these states are concerned MJ is still the devil and your gonna go mad and kill someone....
If it were me in that situation, I would ask if they had a warrant, and if they did'nt, I would suggest that they get one.