A federal judge on Thursday sided with Airbnb and HomeAway and blocked a New York City law that requires the short-term rental platforms to disclose a significant amount of user data.

The preliminary ruling comes in a lawsuit filed against New York City by Airbnb over a new law that requires short-term rental sites to reveal hosts’ data.

Last year, New York passed legislation designed to combat the rise of short-term rentals in the city.

The law prevents landlords and tenants from illegally renting out apartments for a few days at a time to tourists. Additionally, sites like Airbnb would be required to provide the addresses and names of hosts to the city each month, and specify whether rentals are for a whole apartment or just a room.

Airbnb sued over the law, claiming that the ordinance violated users’ privacy rights. HomeAway sued as well, and eventually, the two lawsuits were merged into one.

And Thursday, U.S. District Judge Paul Engelmayer ruled in the short-term rental platforms’ favor, freezing the law’s requirement to disclose user data while the lawsuit is being decided.

The law was due to go into effect next month.

In their case, the short-term rental platforms argue that the city’s ordinance is the result of a “concerted lobbying effort by rival industries aimed at hobbling home-sharing platforms’ ability to do business in New York City.”

Specifically, the sites claim that the hotel industry “pursued a national lobbying campaign with the goal of impairing home-sharing platforms’ ability to compete with traditional hotels.”

The sites also claim that the New York City law violates the First and Fourth Amendments of the Constitution, along with federal and state law.

In handing down the preliminarily ruling, Engelmayer did not decide on the case as a whole, but did rule that the short-term rental platforms’ arguments have some merit.

Despite the setback, New York Mayor Bill de Blasio said that city feels its law and case are on solid legal footing.

From Reuters:

“This is a law to stop landlords from creating de facto hotels, which is unfair and illegal,” New York City Mayor Bill de Blasio said when asked about the decision at a press conference. “We believe we’ll ultimately prevail.”

Airbnb, on the other hand, welcomed the ruling.

“The decision today is a huge win for Airbnb and its users, including the thousands of New Yorkers at risk of illegal surveillance who use Airbnb to help make ends meet," an Airbnb spokesperson said in a statement provided to HousingWire. "The court today recognized the fundamental importance of New Yorkers’ constitutional rights to privacy and the sanctity of their own homes.”

The lawsuit will now proceed to discovery, which is scheduled to be completed within 100 days of the judge’s order.

To read Engelmayer’s ruling in full, click here.

[Update: This article is updated with a statement from Airbnb.]