TALLAHASSEE — The state Supreme Court ruled Friday that legislators and their staffs must testify in a case that accuses Republicans of redrawing political boundaries for partisan advantage in violation of the state Constitution.

The 5-2 decision means that the League of Women Voters, Common Cause and others can force Republican senators and key staff members to testify under oath about their motives in drawing districts. The plaintiffs claim emails show that the GOP plotted with party officials and political consultants for partisan advantage in the 2012 remapping of Senate and congressional districts.

In a blistering dissent, Justice Charles Canady, joined by Chief Justice Ricky Polston, called the majority's conclusions "unprecedented" and said the ruling "grievously violates the constitutional separation of powers."

"For the first time in the recorded history of our Republic, a court has ruled that state legislators are required to submit to interrogation in a civil case concerning their legislative activities," Canady wrote.

The 2012 reapportionment was the first in Florida that had to comply with two voter-approved "fair districts" amendments to the state Constitution that prohibit partisan gerrymandering.

When the groups issued subpoenas on former Senate Majority Leader Andy Gardiner, R-Orlando, and two staffers, the Legislature sought an order to block their testimony as well as access to draft copies of maps.

The Supreme Court majority concluded that the Constitution gives legislators a privilege from testifying, but it "is not absolute and may yield to a compelling, competing interest." In addition, the justices noted, the fair districts amendments specifically outlaw improper legislative "intent," which opened the door for lawmakers and staffs to be forced to testify about their intent.

Justice Barbara Pariente wrote that the court must strike a balance between the constitutional rights of Florida citizens and the separation-of-powers principle that legislators enjoy a shield from being compelled to testify about their activities.

"We conclude that there is no unbending right for legislators and legislative staff members to hide behind a broad assertion of legislative privilege to prevent the discovery of relevant evidence necessary to vindicate the explicit state constitutional prohibition against unconstitutional partisan political gerrymandering and improper discriminatory intent," Pariente wrote.

Deirdre Macnab, president of the League of Women Voters of Florida, praised the decision and said the behind-the-scenes maneuvering over drawing the 2012 districts "made a mockery of open government."

"No amount of kicking and screaming by legislators should prevent the will of the people from being followed," Macnab said.

The Senate and its attorneys declined to comment Friday.

Contact Steve Bousquet at bousquet@tampabaycom or (850) 224-7263.