They are planning these in Oz.
Do NOT turn around. Keep calm and when they pull you over simply ask what the problem is.
If they say..."we are conducting car searches looking for evidence of terrorist activity"...or whatever, simply say..."Do you suspect I have committed a crime or may be on my way to commit a crime?"...when they answer "No"...simply say, "well, i'll be on my way then, have a nice day".
Preferably get them on tape. I have a tape set up ready to place in my car when I get one. I am going to get them on tape and cause a hullabaloo.
Unless Martial Law has been declared the U.S Constitution or indeed just about ANY Western Constitution dictates that Police must have "reasonable" suspicion of illegal activity.
If they go further and state that they are suspicious and within their rights...tell them to write their NAME, BADGE NUMBER, DATE & TIME OF DAY, REASON FOR SEARCH on a peice of paper.
I have nothing against the average copper who has to do these details, they hate them. But you must let the coppers know that if they are going to make your day hard then you are going to make their day hard.
[size=medium]\"The Office\" is the greatest comedy...ever. [/size]