I'd speak to them about it before calling the police.
My across the street neighbors have a long driveway, two car garage, and two spots in front of their house, but for a few years they'd park across my driveway when they were going in the house for a few minutes. Sometimes up to ten min. Never too long, but t was across the driveway, I couldn't get in or out, and my tenants couldn't either .
I spoke to them and just said it's hard to know when I'll be able to get in/out of my driveway and I'm often in a rush and please just park either in your own garage , driveway, or street spots.
They were apologetic and it was a case of it was easier to stop there and run across the street than to turn around :/
Now they don't do it and I didn't have to call the police on them.
I would have if they hadn't listened. But they were reasonable and weren't doing it out of meanness or anything, just my thinking.
Blahhh, I totally feel you on this. Our neighbors to the side constantly have other relatives over and they always park in front of our house. It wouldn't bother me SO much but they were really bad about driving INTO our yard and were constantly busting our sprinkler heads. We finally just had to talk to them and tell them it was a huge problem and it's gotten a little better. Once they realized that H wasn't going to stop what he was doing (weed eating, mowing the lawn, running the sprinkler) a few got the hint and started parking closer to neighbor's house.
Now our neighbor across the street (who we are actually really close to) keeps accumulating more cars - I think they are up to five now - and he's started parking IN our driveway at night when he wants to work on a project in his yard. It annoys the hell out of me because WTH, what if I need to go somewhere? But it's a sticky situation and I don't have a fix.
I'd do like PP's (not all of them, but LOL to some of the suggestions) and just go talk to them and see if y'all can work it out. Hopefully they are reasonable! Good luck!