Three state senators say Indiana's attorney general effectively nullified their votes when he opted not to defend sections of a state immigration law he said were rendered invalid when the U.S. Supreme Court struck down similar sections of an Arizona law.

Republican Senators Mike Delph, Brent Steele and Phil Boots submitted documents Wednesday in U.S. District Court asking Judge Sarah Evans Barker to allow them to defend the parts of the law the attorney general wouldn't.

The attorney general's office said in July it would recommend that Barker strike down most of the portions of the Indiana law that enable police to make warrantless arrests based on certain common immigration documents. It said the high court ruling in June rendered those sections of the Indiana law invalid. Barker already had issued a decision barring the 2011 law from taking effect until she could decide its constitutionality.

The attorney general's office said it would still seek to keep the power to arrest immigrants for whom a 48-hour detention order has been issued.

The senators, who are represented by lawyers from the Immigration Reform Law Institute in Washington, argue in the 16-page motion that the warrantless arrest provisions in the two states' laws are "vastly different." The document claims the Indiana law allows such arrests only in three specific situations that require input from the federal government, unlike the broader powers granted police by the Arizona law. They argue that Indiana's law is consistent with the Supreme Court's Arizona decision.

In the document, the senators, who authored the immigration bill, say they have a right to intervene as defendants because even though the Legislature passed it, the law won't be allowed to take effect if it isn't defended. That effectively robs the lawmakers of their vote, they argue.

Ken Falk, legal director of the American Civil Liberties Union of Indiana, said the civil rights group would oppose letting the senators enter the case.

"We do not believe there is any merit to the intervention request by the three legislators and believe that this further attempt to defend an unconstitutional and misguided law will lead to additional fees and expenses to be borne by the taxpayers of the State of Indiana," Falk said in an email Wednesday.

Attorney general's office spokesman Bryan Corbin said the office respected the senators' views but believed it was the state's sole representative in legal challenges by law and had "vigorously defended" the immigration law until the Supreme Court ruling.

"Now that the U.S. Supreme Court has ruled that warrantless arrest provisions of such laws are unconstitutional, we had a duty to notify the federal court while continuing to defend the portions of the law that are defensible," Corbin said in an email. "It is up to the court as to whether to allow others to intervene at this point."