Law professors from four Louisiana universities are calling for the reversal of a Baton Rouge judge's ruling that upheld a 1976 state law barring felons on probation and parole from voting.

The 17 professors from the law schools at LSU, Southern and Tulane universities, and Loyola University New Orleans are asking the state 1st Circuit Court of Appeal to "protect the constitutional right to vote for the non-incarcerated, including probationers and parolees."

The professors filed what is commonly referred to as a friend of the court brief Thursday in a lawsuit that seeks to strike down the four-decade-old law.

"Because the right to vote is fundamental and essential to the functioning of our democratic society, Louisiana courts must interpret it broadly and resolve any doubt about the scope against the loss of the right," their brief states.

A group called Voice of the Ex-Offender, or VOTE, and eight individual plaintiffs contend in their suit that the state law prevents roughly 71,000 felons on probation and parole from voting.

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State District Judge Tim Kelley reluctantly affirmed the law in March, saying that he agreed with the plaintiffs but could not bend the law.

The 1974 state Constitution prohibits people "under an order of imprisonment" for the conviction of a felony from voting. The '76 law that is being challenged expanded the definition, saying that felons on probation and parole cannot vote.

VOTE and the suit's other plaintiffs argue the time spent "under an order of imprisonment" does not include time spent on probation or parole.

The state maintains that felons on probation or parole are still under an order of imprisonment because they can be sent back to prison if they violate the terms or conditions of their probation or parole.

"The fundamental nature of the right to vote would also support contemporary explanations of limiting 'order of imprisonment' to actual incarceration following conviction," the Louisiana law professors counter in their appeals court brief.

Follow Joe Gyan Jr. on Twitter, @JoeGyanJr.