Can a cop ask you to do anything?

[05GT]

This has yet to happen to me, but I was wondering...
Can a cop pull you over for no reason...
Like say your car is tinted...but you have your front windows down, so he cant tell that you have tint where its illegal.
Can he pull you over for nothing other then he suspects your front windows are tinted...and can he make you roll them up if you get pulled over and they are down?

[undercover]

No, they need a reason to pull you over. They can not pull you over and just inspect your vehicle, however if they have a reason to pull you over and ask you to roll up your window and see tint, sure they could right you.