Better scratch "hoverboards" off your wish list this year if you live in New York City.

The motorized self-balancing scooters are illegal, according to the New York City Police Department and the New York State Department of Motor Vehicles.

The gadgets are considered "electric personal assistive mobility devices."

"They are not considered motor vehicles so they cannot be registered," a DMV spokeswoman told CNNMoney. "According to state law, a first violation shall result in no fine. A second or subsequent violation shall result in a civil fine not to exceed $50."

Hoverboards like the one Marty McFly used in "Back to the Future II" aren't real of course. They're just the name people have given to two-wheeled, self-balancing scooters that look like they are little more than boards with wheels.

A debate about their legality kicked off on Wednesday after the 26th Police Precinct in Harlem deleted a tweet that said "the electric #hoverboard is illegal." This led to a lot of confusion.

The NYPD confirmed to CNNMoney that it considered them illegal in the city. But the department did not respond to followup questions about if or how the law would be enforced.

Self-balancing scooters have become extremely popular over the past year.

They are No. 1 on Amazon's Best Sellers list on the site's Sports and Outdoors section.

There are hundreds of models on sale ranging from about $200 to $2,000.

Celebrities like Wiz Khalifa and Lily Allen have been spotted using them too.

But as more people start riding them around on sidewalks and city streets, police and local authorities have had to define how they should be regulated -- and they don't always agree.

Just last month, British authorities declared them illegal to ride in public because they're considered vehicles, and vehicles can't be driven on sidewalks.