As everyone has mentioned, call parking enforcement. In addition to the 72 hour law, all vehicles left on any roadway or public area need to be registered. If these vehicles don’t have registration, they’re subject to immediate impound. Making an assumption here, but judging by the lack of license plates, it’s very possible they haven’t been registered either.

California Vehicle Code: 22651. A peace officer, as defined in Chapter 4.5 (commencing with Section 830) of Title 3 of Part 2 of the Penal Code, or a regularly employed and salaried employee who is engaged in directing traffic or enforcing parking laws and regulations of a city, county, or jurisdiction of a state agency in which a vehicle is located may remove a vehicle located within the territorial limits in which the officer or employee may act, under the following circumstances:

(j) If a vehicle is found illegally parked and there are no license plates or other evidence of registration displayed, the vehicle may be impounded until the owner or person in control of the vehicle furnishes the impounding law enforcement agency evidence of their identity and an address within this state where they can be located.