I would like to start out by saying I would never do this, because I am lazy, but my curiosity has always been peaked by this scenario. Keeping in mind when I thought this up I was cultivating illegally, so I was breaking the law every second of everyday. I see a car in front of me swerving side to side like a drunk driver. The question is not "Do I call the police?" but "Would calling the police be good or bad karma?" rather. On the one hand, I am getting a potential drunk driver off the road on the other hand I am calling the police and snitching on someone else when I myself am breaking the law and in this situation if what came around went around and someone did the same on me and my growing, I would be none to thrilled. Simple or complex answers, you pick Try not to take it too seriously, like I said, I never called because I was lazy and detest a large chunk of the police force to begin with.
There's a difference between breaking a law that could hurt somebody else, and one that can't. If they're swerving all over the road, they're obviously too drunk to be driving. Or maybe they have their eyes glued to a phone. I don't believe in karma. But if you truly thought this driver is a threat to others, and you did report them, I wouldn't feel too bad about it.
Snitching to protect innocent people is fine. Snitching on someone for a victimless crime is bad. If someone is a serial killer or a child molester then you're damn right they should be "snitched on". You're actually saving innocent people. If someone is selling or smoking weed they aren't hurting anyone. So they should never be snitched on. You're actually hurting someone who wasn't hurting anyone else.
you are comparing a moral decision to a law. sometimes laws actually conflict with morals you aren't comparing apples to apples
There is no duality of karma. Despite how modern western philosophy has warped it. And everyone pretty much gave you your answer already. So I got nothing else to contribute lol