This is an active topic of conversation in the law enforcement community. The changes and adaptations of not being able to catch criminals using the illegality of weed as probable cause.
This was over a decade ago, but I idiotically drove from my "weed legal" home state into a much-less-friendly state... ultimately arrested for flakes found beneath passenger seat (was absolutely sober), in a state where 0.009oz == same "up to 2oz" misdemeanor charges. The police in this tiny Texas town acted like they had caught Pablo Escobar, and not an impoverished college dropout...
For my defense attorney, I chose a well-recommended private attorney (futureMe: I would use the public defender because it would have been the same outcome). His services cost me around a pound of "top shelf" kush. I was broke.
Ultimately I "served my time" [2mo. probation + community service]. Just a few years ago this attorney said to me, in private: "but if we didn't have this legislation [prohibiting marijuana] then I would be out of the job!"
I guess I was supposed to feel bad for his archaic legal practice/funding?