Americans watched -- mostly with approval -- as the Obama administration escalated the use of unmanned aerial vehicles to kill terrorists in foreign lands. Between 2008 and 2010, such attacks in Pakistan nearly quadrupled, and many high-profile terror suspects were killed. Despite the regrettable loss of innocent life in many of the attacks, Americans overwhelmingly (83 percent in a February ABC News/Washington Post poll) approve of their use.

Now drones have generated interest among local and state law enforcement officials, who want to bring them home for nonlethal domestic uses that may not be so popular with the public. Thanks to a law signed by President Obama in February, the Federal Aviation Administration is already developing a plan to make it easier for state and local law enforcement agencies to use drones for surveillance of American citizens, including on their own property.

Congress can and should act now to limit the use of drones and prevent inevitable abuses. It should pass the Preserving Freedom from Unwarranted Surveillance Act, a bill proposed by Sen. Rand Paul, R-Ky., that would limit drone surveillance mostly to cases serious enough to merit a warrant from the courts.

Some argue that warrantless drone searches of private property are constitutionally permissible, just like regular residential flyovers by law enforcement aircraft. But drones are far cheaper and easier to operate for long periods, and they are virtually undetectable. If unchecked, drone surveillance could proliferate to the point of rendering Americans' Fourth Amendment protections weak or even meaningless.

Paul's legislation allows the continued use of drones to patrol the border. It also carves out exceptions for the use of drone surveillance when "necessary to prevent imminent danger to life" or a terrorist attack. But in other cases, law enforcement agencies must obtain warrants from judges before they can deploy drones against American citizens. As Paul puts it, "We should not be treated like criminals or terrorists while we are simply conducting our everyday lives. We should not have our rights infringed upon by unwarranted police-state tactics."

Paul's bill would prohibit the use of evidence obtained by warrantless drone searches in any criminal, civil or regulatory action. It also would empower any person to sue the government for using a drone against him without a warrant. "The judicial branch must have some authority over drones," Paul explains, "as they do with other law enforcement tools."

Drones have the potential to make significant positive contributions to our nation's law enforcement and public safety efforts. They could be deployed in search and rescue operations, against forest fires or to monitor traffic jams. But Americans deserve a proper check on this new government power -- and they deserve it now, before hundreds of drones are already circling our skies and matters truly get out of hand.