Still, the American Civil Liberties Union and other advocacy groups are calling for new protections against what the A.C.L.U. has said could be “routine aerial surveillance of American life.”

Under the new law, within 90 days, the F.A.A. must allow police and first responders to fly drones under 4.4 pounds, as long as they keep them under an altitude of 400 feet and meet other requirements. The agency must also allow for “the safe integration” of all kinds of drones into American airspace, including those for commercial uses, by Sept. 30, 2015. And it must come up with a plan for certifying operators and handling airspace safety issues, among other rules.

The new law, part of a broader financing bill for the F.A.A., came after intense lobbying by drone makers and potential customers.

The agency probably will not be making privacy rules for drones. Although federal law until now had prohibited drones except for recreational use or for some waiver-specific law enforcement purposes, the agency has issued only warnings, never penalties, for unauthorized uses, a spokeswoman said. The agency was reviewing the law’s language, the spokeswoman said.

For drone makers, the change in the law comes at a particularly good time. With the winding-down of the war in Afghanistan, where drones have been used to gather intelligence and fire missiles, these manufacturers have been awaiting lucrative new opportunities at home. The market for drones is valued at $5.9 billion and is expected to double in the next decade, according to industry figures. Drones can cost millions of dollars for the most sophisticated varieties to as little as $300 for one that can be piloted from an iPhone.

“We see a huge potential market,” said Ben Gielow of the Association for Unmanned Vehicle Systems International, a drone maker trade group.