Idaho's Republican lawmakers have sent a tax conformity bill back to the drawing board because it would have removed an unenforceable rule banning joint returns from same-sex couples.

Members of the Idaho House of Representatives voted 54-15 Thursday to send the bill back to committee. The legislation is brought annually to make the state's tax code conform with changes to federal tax code. This year's version sought to remove a requirement for same-sex couples to file separate state tax returns. That requirement is now void because the U.S. Supreme Court rules last year that states can't enforce gay marriage bans.

"There has been some objection to this particular piece of legislation," said House Revenue and Taxation Committee Chairman Gary Collins of Nampa. "We have been working on trying to get some type of a consensus."

Tax conformity bills are rarely controversial, with most disagreements centered on how much it'll cost the state to conform to new federal rules approved by Congress.

However, HB 354 had already attracted heated outcries from constituents to House lawmakers two days after the vote was sent to the floor. The 2016 Legislature is currently in an election year, which means lawmakers tend to be skittish voting on bills that will tick off their legislative districts and send them voting for competing candidates.

"A vote for this is a vote against the Constitution of our state as written," wrote Russell Spriggs, an Idaho NRA instructor, in an email sent to the entire House. "I will personally consider a vote against our Constitution, by individually accountable individuals we have elected to represent us, as an act of treason."

Another email warned that "God will not be on your side" if the bill passed.

"The arguments that we're seeing from folks in the pressure-point emails that we're getting is not what this legislation is about," said House Minority Assistant Leader Mat Erpelding of Boise.

Lawmakers usually prefer to sync the state's tax code with the federal version to make it easier for residents and businesses to do their taxes or avoid having to keep separate accounting books to track the different rules.

Rep. Heather Scott of Blanchard was the only Republican to vote against sending the bill back to committee, even though she cast one of the few nay votes to send the measure to the House floor because of the gay marriage-specific provision.

"I was ready to vote on the bill today," Scott told The Associated Press, declining to explain her vote any further.

A new version of the bill has been scheduled to be introduced on Friday.