Sometimes cops twist words around to make it seem like they are telling you they are going to search your car, when really they're asking your permission. By not answering, you are giving them permission to search your car. All you have to do is refuse to give them consent and without probable cause they cannot search you. Of course, if they try to anyway, go ahead and step out of their way (they have a gun.. be reasonable) but take them up in court. Hell, with matters this simple you may not even need a lawyer. Often times though a cop will try and bullshit some probable cause; just remember: you are innocent until proven guilty.