The Tennessee Court of Appeals on Friday ruled that the Nashville vote that created a civilian board with the power to investigate police was legitimate, rejecting the police union's challenge and clearing the way for the board to begin work.

In the ruling, the Court of Appeals sided with the Davidson County Circuit Court, which threw out the challenge in September. Nashville voters in November approved the formation of a community oversight board while the appeal was pending.

Advocacy group Community Oversight Now gathered signatures to put the issue on the Nov. 6 ballot.

But Nashville's chapter of the Fraternal Order of Police challenged the vote as illegitimate, saying the group had not met the signature threshold needed to get a measure added to the ballot.

The FOP's argument was rejected by the Davidson County Election Commission, the Circuit Court and now the Court of Appeals.

What to know:Nashville approves police oversight board

“The FOP’s attempt to invalidate a free election and strip 134,135 people of their vote has been rejected yet again," Community Oversight Now attorneys Jamie Hollin and Daniel Horwitz said in a statement. "We are pleased that Metro’s Community Oversight Board will be permitted to do the important work that voters demanded.”

FOP lawyer David Raybin said the group planned to appeal the case to the Tennessee Supreme Court.

“We respectfully believe that the required number of ballots is an important issue the Supreme Court should review,” he said in a statement. “We will now proceed to appeal to our highest court for a final resolution of the question.”

Legal argument

The debate hinged on a dense dispute over city laws.

The Metro Charter allows voters to consider a potential amendment if a petition is signed by 10 percent of the turnout in the "preceding general election."

City and Community Oversight Now lawyers said it was the low-turnout city election in August 2016, when 47,074 people voted. That made the petition threshold 4,708.

The FOP said a higher turnout election should be used to guide the threshold.

The appeals court sided with the city and advocacy group.

"We conclude, as did the trial court, that the proper election to use to calculate the number of signatures required on the referendum petition, the preceding general election, was the election held on August 4, 2016," the court said in its ruling.

The Metro Council is set to finalize the membership of the oversight board later this month. The oversight board has caught the eye of the Republican-dominated state legislature, raising the possibility of intervention on the issue during the 2019 session.

Reach Adam Tamburin at 615-726-5986 and atamburin@tennessean.com. Follow him on Twitter @tamburintweets.