Ready or not, the drones are coming home: Nine law enforcement agencies in six states already use drones, and another nine have applied to the Federal Aviation Administration for permission to do the same. So far, police agencies have not used drones for general surveillance, but lawmakers in nearly half the states are looking to enhance privacy protections before drones become standard policing.

Most state legislators don’t object to the military use of drones overseas, and they are largely at peace with university researchers or farmers using them here to spray crops or deliver animal feed. But they cringe at the possibility that domestic police forces will violate people’s privacy by using them in regular policing.

At least 21 states are debating bills to limit drone use, according to the American Civil Liberties Union. The proposals range from requiring police to obtain a search warrant before using a drone, to placing a moratorium on any drone use by law enforcement. And last week, a bipartisan group of U.S. House members introduced a bill that would require a warrant for drone use in criminal investigations.