Salt Lake City ? Mayor Rocky Anderson wants to let domestic partners in Salt Lake City document their relationships, saying a registry would allow people to signify “they are partners, that they formed a domestic partnership.”

But whether he can legally do that in Utah is up for debate.

Some critics say such a move would run afoul of a state law approved by the largely conservative Utah electorate last year. The city’s attorney is still researching the law’s implications and whether it would block Anderson’s plan.

The ballot initiative approved by voters last year changed the state constitution to say “no other domestic union, however denominated, may be recognized as a marriage or given the same or substantially equivalent legal effect.”

Republican State Rep. LaVar Christensen, who backed the ballot initiative, said he was willing to sponsor legislation to stop the city if the current law isn’t clear.

Anderson’s “attempt to circumvent existing law is tantamount to the San Francisco mayor standing on the steps (of City Hall) and performing (gay) marriages,” Christensen said.

Anderson also is considering extending health benefits to partners of gay employees, something proponents of the law say the city is prevented from doing.