I don't usually do criminal law, but the senior lawyer I was working for needed help on a "friends & family" case. Three high school kids had been busted for underage drinking. They had, in fact, been drinking at a party.
For whatever reason, the local township where they were arrested wanted to throw the book at them under a local ordinance. IIRC, the kids just pled guilty (we weren't involved at that time) but ended up getting every punishment possible - hefty fines, community service, and the kicker which was having their drivers licenses revoked, even though they hadn't been DUI.
The families came to the firm for help after the sentence, because it had been a graduation party and the kids were now starting college. Unable to drive, their parents were bringing them to and from campus every day, and driving them everywhere else. This was a huge burden on the family, and the parents were desperate for any help. So an appeal from the municipal court was taken...by two of the kids. The third decided it was pointless and he'd take his lumps.
I'm researching the local ordinance to see why they got hit so hard, and I start wondering how it was that the township could determine that they'd lose their licenses. Seemed to me that was a state function, not local, and I didn't usually see superior levels of government ceding decisions like that to lower levels. So I tracked down the state law about what authority municipalities had.
It turned out, there was a very explicit state law limiting what criminal penalties a municipality could impose...and nearly every part of the local underage drinking law exceeded those penalties.
So, I drafted a quick brief arguing that the convictions had to be overturned because Podunk Township simply didn't have the authority to take away licenses (or impose fines as large as they did), and the law was invalid. I went to the hearing assuming I'd missed something obvious. Turns out, I hadn't. The judge asked the township attorney why we were wrong and he just shrugged and said "I think I have to have a talk with the Commissioners about this one."
The judge asked him if he had any argument why he shouldn't toss the convictions on the grounds that the city didn't have that authority. Again...no argument. He didn't even seem all that bothered by it.
So, the convictions were tossed. No record, no penalties, licenses restored. The families were over the moon...and as far as I know, the third kid who had decided not to appeal, had to keep getting driven to college.
If the kids had been charged under the state law about underage drinking, rather than the municipal ordinance, none of this would have happened - but they'd wanted to set an example I guess.