Our neighborhood Teshole is solving the problem by parking across the sidewalk. They do have a garage, but that's for storing their other car.
Since I've never met them, I'm still pondering the best way to address the problem. Cops, anonymous note, signed note, each have their drawbacks. So for the time being, I content myself with passive aggressive whining to third parties.
Seriously, let them sort it out. It's their job. They will likely give them a warning the first time, depending on the department. Mine would.