Inconsiderate neighbor w/ 7-8 cars

Neighbor (1 individual) has been parking 7-8 cars on the block essentially taking up 1/3 of the parking spots on the block. He does not drive these vehicles and every few weeks gets rotated with different cars. When he does use one of the vehicles, he’ll back up another car to park in between 2 spots so he can save it when he returns. It’s completely infuriating. I’ve called parking authority and they’ve indicated there is no limit # of passes an individual can get so nothing can be done as long as they have valid permits. I suspect this person is flipping these vehicles and using public street as his personal parking lot. Any one else confront a similar situation and/or advise how best to proceed?