GREENBELT, Md. (AP) — News outlets filed a lawsuit on Friday challenging a Maryland law meant to fight foreign meddling in online political advertising because they say it creates unfair burdens on media sites that publish such ads.

The Maryland-Delaware-D.C. Press Association and several newspapers, including The Washington Post and The Baltimore Sun, filed the federal lawsuit challenging the constitutionality of the legislation passed in April. The law went into effect without the signature of the governor, who had concerns about its requirements.

The challengers argue the law infringes on free speech because it requires them to publish information about political ad buyers. The newspapers also say the law includes onerous requirements for them to make data on ad buyers available to election officials on request.

The lawsuit states that "there is a stark difference between requiring speakers to disclose who they are and the source of their funding, and imposing that burden on newspapers and other Internet publishers, especially in the circumstances here."

The plaintiffs asked for an expedited court schedule because they say the state won't delay the rules while the lawsuit plays out.

A spokeswoman for state Attorney General Brian Frosh declined comment on the lawsuit, as did the office of the administrator of the Maryland Board of Elections. Both are named as defendants.

Supporters of the measure said it was the first of its kind in the country because of the powers it gave the attorney general and elections officials. New York also enacted a measure this year to increase transparency for online political ads.

A sponsor of the law, Maryland Delegate Alonzo Washington, had argued in February that the law would provide greater accountability and transparency for ads on social media platforms. He cited online political ad buys linked to Russia during the 2016 election cycle.

But Maryland's Republican Gov. Larry Hogan expressed concerns about the legislation, and declined to sign it. He said that while the law had admirable goals, he was concerned about its constitutionality because of the requirements it would put on media organizations.