Earlier this month the California State Assembly voted to require police to obtain warrants to use drones for surveillance except in exigent circumstances. Now the State Senate has handily passed the legislation with a 25 to 8 vote. The bill would require the police to obtain a search warrant based on probable cause before using a drone for surveillance.

When the Assembly passed the bill, some astute Reason commenters wondered if police do not have to obtain a warrant for helicopter surveillance, why should they be required to get one for drone surveillance? In the 1989 case Florida v. Riley, the U.S. Supreme Court ruled that since airplanes and helicopters often fly over private property that citizens do not have a reasonable expectation of privacy that their activities will not be observed from the air. Consequently, the police were permitted use evidence obtained without a search warrant from helicopter observation of a greenhouse in which they suspected marijuana was being grown.

Despite this disappointing Supreme Court decision, citizens, nevertheless, could generally count on the fact that police would not be resorting to extensive aerial surveillance due to the cost and trouble in arranging for helicopter flights. That would no longer be the case with development of inexpensive drones.

What the California legislation does is establish that citizens do, in effect, have a reasonable expectation that they will be free of pervasive police drone surveillance. Hooray! Every state should pass such bans as speedily as possible.