Shipping merchandise via drones could be revolutionary for e-commerce companies--but getting them off the ground is going to be a tough slog.

U.S. lawmakers are close to delivering a draft of the Federal Aviation Authority's reauthorization bill, which will include rules for nonmilitary drones, and drone opponents are lobbying hard against the unmanned flying machines, The New York Times reports. Why? Critics argue that creating a pathway for increased drone use will lead to significant safety and privacy risks.

On the other side, companies like Amazon and Google are urging lawmakers to allow for testing of delivery drones in areas with relatively sparse populations. Here are three reasons why making the case for delivery drones could be a hard sell.

1. The F.A.A. is moving to keep delivery drones grounded.

Delivery drones are currently restricted, and rules proposed by the F.A.A. would keep them "grounded for the foreseeable future," according to the Times. Though one lobbyist representing Amazon expects new regulations to come gradually, rather than a single ruling banning delivery or making its widespread use legal, the next set of rules, anticipated as early as February, are not expected to allow for delivery. 

2. Legal drones are already causing significant problems.

Recreational drones have been secretly dropping contraband over prison walls at night in at least least five U.S. states, the AP reports. The problem has led republican legislators in Wisconsin to introduce a bill that would allow counties and municipalities to establish no-fly zones for drones. Separately, an F.A.A. mandate introduced last month requiring all recreational drones weighing .5 pounds or more to be registered appears to have fallen massively short. Though the mandate registered some 300,000 drones in a database, it is estimated that between 700,000 and 1 million individuals received drones as Christmas gifts last month. 

3. Congress is seriously concerned about drone safety.

Florida senator Bill Nelson, the highest-ranking democrat on the committee overseeing the F.A.A. reauthorization bill, is calling in the big guns to coordinate drone safety regulation. Nelson has written letters to the F.A.A., Homeland Security, NASA, and the Pentagon asking for their collaboration on establishing safety rules. Why? Nelson has cited the specific threat posed by drones flying near airports and prisons and is asking the four agencies to help "mitigate the risk," the Times reports.

Though navigational technology preventing drones from flying too close to specific objects or designates areas could help prevent many drone-related risks, companies like Amazon and Google may have a long fight before their vision of drones dropping packages on U.S. doorsteps becomes a reality.