Local drone laws can often be tougher than national laws, with some threatening jail time.
You may want to think twice about where you fly a drone the next time you travel across the U.S.
Although the Federal Aviation Administration is in charge of regulating drones—as it regulates conventional airplanes—numerous states and local governments have been enacting their own drone rules. In some cases, these local drone laws conflict with the FAA’s drone rules, resulting in hefty fines and even jail time even though the pilot may not be violating federal laws.
That’s one of the takeaways from new research on drone laws published Tuesday by research group The Center for the Study of the Drone at Bard College. The authors of the report examined several local drone ordinances established in recent years and discovered that 135 localities in 31 states have passed drone rules that impact over 30 million people living in those areas.
Get Data Sheet, Fortune’s technology newsletter.
Additionally, the report said that 24 localities list “jail time as a possible punishment” for violating their drone laws, even though the FAA considers those rules to be preemptable, meaning that the FAA believes that the federal law should overrule them.
“The proliferation of these rules could have a destabilizing affect on the integration process,” said center co-director Arthur Holland Michel in regards to creating a national airspace for drones. “It will be very hard to maintain a coordinated national airspace system with what the FAA describes as a patchwork quilt of local regulations.”
The FAA’s current drone rules require hobbyists to register their drones in a national registry, fly the drones within their line of sight, and avoid restricted areas like airports or stadiums during sporting events. The FAA also created an app for people to see where they should or shouldn’t be flying their drones.
However, many of the local governments that created their own drone rules believe that the federal government’s current rules do not adequately address issues like privacy, trespassing, and flying drones over another person’s property, Michel said.
In Aventura, Fla., for example, drone operators could face a $500 fine and up to a year in jail if they fly a drone at a public gathering or take photos of a person’s house without their consent. In Beachwood, N.J., a person can be fined up to $1,000 and spend up to 90 days in jail for violating a similar drone law.
Michel said that these local drone laws could impact business owners who use drones for purposes like inspecting rooftops for real estate projects. In these cases, the drone operator could record the adjacent property next to the home they are taking pictures of, which may result in a violation of the rules.
Michel said part of the inspiration for the drone study stemmed from a barbecue with friends in Long Island. As he was chatting with people at the party, he realized that if he flew a drone to a nearby town, he “would suddenly be violating these rules and potentially face a punishment.”
“When you look up at the airspace you don’t see any barriers,” said Michel. “It is one big fabric, so to speak.”
It should be noted that while these local governments have enacted tough laws, “there have been very few cases of people jailed for drone use,” he said. In February, a Seattle man was sentenced to 30 days in jail and a $500 fine when his drone accidentally hit a woman during a 2015 parade, in what was a rare occurrence of someone being arrested for recklessly flying drones.
However, the often-conflicting local and federal drone rules pose potential problems if there is a legal dispute that puts the local government against federal authorities, Michel explained. The potential legal dilemmas may only worsen as the FAA attempts to establish a national drone air traffic management system with the help of NASA.
For more about finance and technology, watch:
The FAA is “going to want a level of uniformity around the country in terms of the airspace that will probably run up against the many localities that see it as their rights to protect their citizens,” Michel said.