Opponents of a new Maryland law that would give undocumented immigrants breaks on in-state college tuition have no right to force a referendum, an immigrant rights group charged Monday in a lawsuit seeking to keep the issue off the 2012 ballot.

Casa of Maryland, a group often allied with the state’s Democratic leaders, alleges that state elections officials erred in letting opponents collect signatures to suspend the Maryland DREAM Act, the first state law in 20 years to be halted and sent to the ballot by a petition drive.

The lawsuit contends that tax money the DREAM Act would direct to tuition aid for undocumented immigrants effectively puts the measure in a class of laws dealing with state budget issues, making it off-limits to a referendum.

If the measure was eligible for the ballot, the lawsuit asserts another flaw. It says opponents do not have enough valid signatures, primarily because those that were collected using new Internet software should be thrown out.

The online tool was developed this year by a Maryland Republican lawmaker in anticipation of a future ballot-box fight over same-sex marriage. It helped nearly 44,000 voters print and file petitions with their names, addresses and other information listed exactly as recorded in state voter rolls.Such precision is essential because any discrepancy can invalidate a petitioner’s signature.

The tool helped a small group of conservative organizers shatter previous records for statewide signature gathering and has emboldened Maryland’s Republican minority, with some lawmakers already threatening to use the ballot box routinely as a check on the state’s Democratic-controlled General Assembly.

The prospect of such efforts makes the integrity of the new system all the more important, said one of the lawyers challenging the petition.

“There’s no safeguard. If someone knows your name, Zip code and date of birth, which might be on your Facebook page, the computer will print out that information exactly,” said Joseph E. Sandler, a top election-law lawyer and former general counsel for the Democratic National Committee, whose firm is litigating the case pro bono for the plaintiffs. “There is no way to make sure the voter whose name appears on the petition is the one who printed it out and signed it.

“Maryland law makes this deliberately difficult,” Sandler added. “We live in a representative democracy. We don’t live by mob rule; not every law is supposed to go to the voters.”

Del. Patrick McDonough, a Baltimore County Republican who was a lead organizer of the petition drive, called the lawsuit a “shameful” attempt to upend the will of voters and petition signers.

He said it was ludicrous for proponents to argue that the DREAM Act was primarily a budget law and not a new state policy, which would be subject to referendum.

McDonough also singled out Casa of Maryland, saying the organization was seeking to circumvent the state’s election rules to “promote the best interests of illegal aliens.”

Casa stressed that affected students and teachers are the lead plaintiffs. The first two are listed as John Doe and Jane Doe, both 18-year-old undocumented immigrants. The suit says the two excelled in Maryland high schools and may not be able to afford tuition at Baltimore City Community College this fall without in-state rates. The suit says their identities were kept confidential to protect them from harassment.

Under the law, which passed in April after years of wrangling, undocumented immigrants — who are able to prove that they have attended high school in Maryland for at least three years and that their parents or guardians have begun filing taxes — were to have been allowed to begin courses this fall at community colleges at in-state rates. After earning associates degrees, they would be eligible for in-state rates at University of Maryland system schools.

Amy Exelby, deputy executive director of the left-leaning Ballot Initiative Strategy Center, said the Maryland case is special. Utah and California have faced recent legal action over Internet tools that allow voters to electronically sign petitions, but they have not involved printing petitions.

“States are taking a slow, cautious approach to this,” she said. The chance for the court to review the online petitions in Maryland, she said, “is good for democracy.”