Neighbor is blocking parking around house--is this legal?

I cannot find a straight answer via google, hoping someone might know the answer here. Neighbors are on a corner property behind my mother's condo building. They have bricked off the entire area around their house and have a towing company's sign up in their driveway. They have been very aggressive about towing anyone who parks on the street around their house--I would go as far as saying it is an obsession. They do not use any of the spaces they have blocked off. They have made it very clear they do not like anyone who lives in the building even though it was there before they moved in. This has been going on for years. If anyone knows if this is legal or if there is anything that can be done input would be very much appreciated. Thank you! via /r/SeattleWA http://ift.tt/2eePHoq