WASHINGTON — New Jersey’s attorney general has gone to court to find out why President Donald Trump’s Justice Department changed its mind and now is threatening the state’s $350 million online gambling industry.

Attorney General Gurbir S. Grewal filed suit in U.S. District Court in New Jersey Tuesday.

He acted after Justice failed to turn over documents that could show whether the action was in response to lobbying efforts by Sheldon Adelson, a major Trump supporter. Grewal filed a Freedom of Information Act request in February but said he never received any materials.

The casino billionaire and his wife spent almost $200 million to help elect Trump and congressional Republicans in the last two elections. That was more than anyone else, according to the Center for Responsive Politics, a Washington-based research group.

“Online gaming is an important part of New Jersey’s economy, and the residents of New Jersey deserve to know why the Justice Department is threatening to come after an industry we legalized years ago,” Grewal said.

“It’s especially important that we figure out whether this federal crackdown is the result of a lobbying campaign by a single individual seeking to protect his personal business interests.”

Justice Department spokeswoman Kelly Laco declined comment.

Adelson, head of the Las Vegas Sands Corp., has fought online gambling even as other major casino companies such as MGM and Caesars Entertainment have embraced it and opened sites for New Jersey residents.

He is the power behind the Coalition to Stop Online Gambling, an advocacy group.

The Justice Department under President Barack Obama ruled in 2011 that the Wire Act did not ban in-state online gambling, thus paving the way for New Jersey-based casinos to allow state residents to bet over the Internet.

The industry has grown to become a $352.7 million a year business and contributes $60 million in taxes. Along with sports betting, online gambling has helped boost an Atlantic City casino industry that fell on hard times in recent years.

But Trump’s Justice Department reversed its position in January, allowing federal prosecutors to begin enforcing a ban beginning June 14 even in states that allow online gambling.

Trump and Vice President Mike Pence both traveled to Las Vegas last month to attend the Republican Jewish Coalition’s annual leadership meeting. Adelson, a major supporter of the group, met privately with Trump at the conference.

Last November, Trump gave Miriam Adelson the Presidential Medal of Freedom, the nation’s highest civilian honor.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.

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