I live in Virginia and yes, I was referring to a regular traffic stop. In terms of probable cause here, it seems to be based on what you say. Most people here believe that an officer smelling something is probable cause (kind of like the billowing smoke) but in my research and understanding based on an explanation from an attorney (could be dishonest I know), if an officer in VA says he smells marijuana or something and you do not refute it, he now has probable cause. The key when an officers says he smells something is to basically say "huh, well I don't smell anything officer" and this no longer presents probable cause, the reason being that a smell can't be taken to court and just because something smells like marijuana doesn't mean it is marijuana. This reasoning seems kind of stupid to me but apparently that is the correct action when smell or a smoke cloud comes billowing out of your car. Once again though this all depends on the officer playing by the rules also, which is why I'll state again; when dealing with police, use a video camera if you want 100% fair representation if charges should arise from your interaction.