Attorney General Martha Coakley erred in excluding from the November state ballot a question that calls for the repeal of the 2011 gambling law, and voters should have the right to decide the issue, casino opponents contended in a court filing Friday.

The group Repeal the Casino Deal submitted a 53-page brief with the Supreme Judicial Court, which is expected to hear arguments in early May.

Former Attorney General Scott Harshbarger, a leader of the anti-casino movement, said that while he greatly respected Coakley, she was "simply wrong" in her analysis of the repeal petition. He said it was inevitable the question would ultimately appear on the ballot.

The casino law allows for up to three resort casinos and one slots parlor and created the Massachusetts Gaming Commission to award licenses and regulate future gambling.

All proposed ballot questions must first go through the attorney general's office to determine whether they pass constitutional muster. In last fall's ruling, Coakley said the repeal question would violate the contracts clause of the state constitution by permitting voters to interfere with implied contracts between the commission and applicants for casino licenses.

"The proposed law is therefore inconsistent with the right to receive compensation for private property appropriated to public use and cannot be certified," the attorney general wrote.

Repeal the Casino Deal argued in its filing that in passing the law, the Legislature did not intend to create any contracts between the commission and casino applicants that would ever prevent the state from exercising its policing or regulatory powers over gambling.