Legal Question in Construction Law in California

I'd think it would be illegal if it's a public street. Streets are put there for the passage and parking of motor vehicles. Ordinances affecting the permitted uses of streets will vary from town to town, but I'd be quite surprised if there weren't some ordinance that would make the placement of a large and immobile device in a street illegal. If the street is private, as it may be in a gated neighborhood, it's less likely to be "illegal" in the strict sense of the term, but is likely to be contrary to some CC&R or other (non-statutory) rule of a neighborhood association or HOA. Also, basically, the street isn't your private property, and you don't have any greater right to use it than whatever right is granted you by the owner or controlling body (city, HOA, etc.) that is in charge of the street. Parking a basketball hoop or anything else without a duly-issued license plate is goinf to run afoul of some law, ordinance, rule or regulation.