Driving without headlights on = Ridiculous overtaken actions

So this is the second time ive even been pulled over. i just stopped at a scnoco to grab my supplies. for whatever reason i didnt put my headlights on when i went on to the main street, ive neeever done that be4 no matter how messed up i was. so the cop pulls me over. smelled some pot so he asked me to spet out of the car. he got my license, along with my friends who was with my at the time. ended up calling a K-9 unit to check my car. they found nothing except for a K2 spice pack that was in my car for like a year and now its legal so i get hit with pary (gay), and my registration on the car has juuuust ran up, so they took me car! just took it and told me and my friend to walk home. omg they were such asses >.< i wish marijuana was legal so all this stupid shit would stop. it sucked =\

 

How would marijuana being legal stop you being pulled over for driving without headlights on, driving under the influence and having your car impounded for expired registration?