New York City may no longer be battling Airbnb over its law against short-term rentals of apartments, but its enforcement may make enemies out of what could be its biggest allies.

This year, the city started enforcing the law establishing fines for short-term rentals of full apartments (rather than listing a spare bedroom in an apartment the Airbnb host lives in), but landlords who have reported tenants for using Airbnb have seen themselves fined for illegal usage of units they own, Crain's reports.

In 2015, AIMCO reported a tenant at 120 West 23rd St. to the Mayor's Office of Special Enforcement, rather than pursue a lawsuit. The tenant had installed bunk beds in the unit and posted to Airbnb. The office issued an order to vacate, but also fined AIMCO $3,400. A court case with multiple appeals was eventually decided in favor of the New York City Department of Buildings, holding landlords responsible for any illegal usage of their apartments, even when the usage is tenant-made.

“We urge all New Yorkers to report violations of the law, including those that create dangerous living conditions,” a spokesman for the DOB said. “But reporting violations by others does not mean landlords are shielded from their own legal duty of providing safe homes to paying tenants.”

The policy of going after landlords and tenants alike could have a chilling effect on landlords who wish to report Airbnb postings in their units, removing a vital first step in the city's goal to prevent illegal short-term rentals.

“If you want us to cooperate with you, you have to stop fining us,” Jeffrey Goldman, a partner at Belkin Burden Wenig & Goldman who specializes in representing landlords, told Crain's.