NEW YORK, Aug 11 (Reuters) - A New York state judge has allowed a group of 15 individuals to take part in a lawsuit over where prisoners are counted for redistricting purposes.

The 15 people are supporters of a 2010 law that counts prisoners as residents of the communities where they lived before incarceration instead of the communities where they are detained.

Supreme Court Justice Eugene Devine gave the individuals permission to intervene as defendants in the lawsuit, which seeks to overturn the 2010 law.

The lawsuit was filed by state senators and voters on April 4. The plaintiffs claimed the legislation dilutes the voter weighting of Republican districts in upstate New York and shifts them to Democratic districts around New York city. They argued that the 15 individuals should not be allowed to intervene because they had no bona fide interest in the case.

Devine disagreed. "While plaintiffs strongly urge the Court to deny intervention, arguing, in part, that these voters do not have a bona fide interest in this suit, the Court rejects this position," Devine wrote.

"Several plaintiffs appearing in this action are similarly situated to the individual intervenors -- both groups are voters that may be affected by inmate residential status," Devine wrote.

The original defendants in the case were New York State Legislative Task Force on Demographic Research and Reapportionment and the sate Department of Correctional Services. The task force develops the state's redistricting plans and the corrections department provides prison residential data to the task force.

The plaintiffs want the judge to declare the law unconstitutional and issue a permanent injunction to prevent the task force and corrections department from acting on it.

Not counting prisoners as residents of their home communities would cost those areas -- which are often minority communities -- equal representation, Dale Ho, an attorney for the NAACP Legal Defense and Education Fund, has said.

In allowing them into the case, Devine had to consider whether their interests were adequately represented. Correctional Services' mission is not to ensure the protection of minority voting or to help create a more equitable districting system, the decision said.

The task force has not made a formal submission in the lawsuit, asking only that the judge render a decision without delay so that it knows how to proceed.

In his ruling, Devine refused to allow three advocacy groups -- NAACP New York State Conference; Voices of Community Activists and Leaders-New York; and Common Cause of New York -- to intervene. He said the outcome of the litigation will not impact their ability to advocate on behalf of minority voters.

The Brennan Center for Justice at NYU School of Law, one of the groups representing the intervenors, welcomed the decision to allow the individuals to intervene.

"We want to make sure that this law is adequately defended by people who have a stake in the matter and care to ensure that New Yorkers' voting rights aren't unfairly distorted," said Wendy Weiser, a lawyer with the center.

Plaintiffs' attorney David Lewis did not return a call for comment.

The case is Senator Elizabeth O'C. Little et al v. New York State Task Force on Demographic Research and Reapportionment et al, New York Supreme Court, Albany County, No. 2310-2011.

For Little et al: David Lewis.

For New York State Department of Correctional Services: Attorney General of the State of New York.

(Reporting by Jennifer Golson)

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