Works like this, cop gets told to look out for your car. He sees you and follows you, sooner or later you do something that let's him justify pulling you over then he asks you a bunch of questions and decides you are acting nervous, or smells alcohol, or smells pot. Then he either convinces you to let him search your car or he gets a dog to come say it smells drugs, or and this is my favorite he gets you upset by getting in your personal space and amping you up, then when he quickly reaches for your arm and you jerk away he can arrest you for resisting. Then they search the car to make sure everything is documented for impound, then they seize money and expensive things to make sure it isn't connected to any crimes.

Charges against you get dropped or you plead to something lesser and you walk, but now you have to prove that your shit was legally yours.