Maryland conservatives had no right to halt a new state law that would give undocumented immigrants in-state college tuition breaks, an immigrant-rights group charged Monday in a lawsuit seeking to keep the issue off the 2012 ballot.

Casa de Maryland, a group backed by the state’s Democratic leaders and derided by its Republican minority, alleged in its filing that state elections officials erred in letting conservatives collect signatures to force a statewide referendum on the Maryland DREAM Act, the state’s first law petitioned to the ballot in 20 years.

Lawyers for the group contend that the tax money that the law would set aside for undocumented immigrants effectively puts the measure in a class of laws dealing with state budget issues, making it off-limits to voter referendum.

The group also contends that nearly 44,000 signatures collected using a new online tool, which was designed to let voters print out their names, addresses, and other information exactly as they appear on state voter rolls to limit mistakes, should be invalidated because voters themselves did not write in the information.

The lawsuit contends that without the online petition signatures, as well as many others collected by hand that it says also contain errors, opponents would not have reached the threshold to qualify the measure for the ballot.

The lawsuit seeks to restore the law immediately. In addition to Casa de Maryland, the suit has eight individual plaintiffs. The lead two are undocumented immigrants listed as John Doe and Jane Doe, which the suit alleges would not be able to afford community college this fall in Maryland without the state aid.

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. In a statement he said it was nonsense for proponents to contend that the DREAM Act was a budget issue and not a new policy and he attacked Casa de Maryland for taking the issue to court.

“Once again Casa has proven they are against the Rule of Law, disrespect the right of citizens to petition their government and willing to use Taxpayer funds to promote the best interest of Illegal Aliens.”

Under the law, which did not take effect last month because of the petition drive, undocumented immigrants who can prove that they have attended Maryland high schools 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. The measure was approved in the closing hours of this year’s legislative session after years of failed attempts.