Republican U.S. Senators Jon Kyl of Arizona and Orrin Hatch of Utah, both longtime foes of sports gambling, are asking U.S. Attorney General Eric Holder to probe the recent Delaware law authorizing sports betting.

In a letter to the attorney general, the senators also asked Holder to prepare a defense against a pending lawsuit from New Jersey lawmakers challenging the federal ban on sports betting implemented in 1992.

The 1992 Professional and Amateur Sports Protection Act banned sports betting in all states but Delaware, Nevada, Montana and Oregon.

Delaware was grandfathered in because of a sports lottery the state ran in the 1970s. The state’s lawmakers recently approved single-game and parlay sports betting, and operators of the three Delaware racinos plan to have sports books in place in time for the start of the NFL season.

Kyl and Hatch claim the single-game betting is not legal, because it was not part of the 1970s sports lottery under which Delaware was exempted from the 1992 law. “It is our hope that the Department of Justice will monitor closely the situation in Delaware to ensure the state’s compliance with federal law,” the senators wrote in the letter to Holder, obtained by the Associated Press.

Also last month, the major sports leagues in the United States sued the state using the same arguments the senators have employed.