In reply to Duncan Bourne:
I guess that is why they hang around after clamping you thesedays, so you are less inclined to remove the clamp yourself. However, they can not physically stop you so if you have a mate with you they can video the proceedings on their phone. Alternativly perhaps we have found what 4x4s are actually good for, those massive wheels must be impossible to clamp.
If you wanted to be really pedantic, it'd be funny to watch their faces as you remove all 4 wheels leaving your car stood on axle stands :-D