Updated

The mayor of Salt Lake City signed an executive order Wednesday granting domestic partner benefits to city workers, a decision that is likely to be challenged, if not in the courts then in the Legislature.

The city estimates up to 30 of its 2,600 employees, about 1 percent, will sign up for the option, adding about $113,000 a year to its costs.

"This is an important step toward recognizing the needs and equality of all city employees," Mayor Rocky Anderson (search) said. "Providing benefits to families, without discriminating on the basis of marital status or sexual orientation, will provide very real benefits to both the adults and children in employees' families."

The order is in effect immediately, but the benefits can't begin until the city amends its contracts with insurance providers.

The city's insurance administrator, the Public Employees Health Program, has indicated it wants a judge's opinion on the legality of the order before taking that step.

At least one state lawmaker has said he believes domestic partner benefits are illegal in Utah. If they aren't, Republican state Rep. LaVar Christensen (search) said, he will introduce legislation next year to make them illegal.

But Anderson spokesman Cliff Lyon said the mayor is confident the order would be upheld if challenged.

"We've had this thoroughly researched by our legal department, which is not an insubstantial group of people, knowing full well it would be challenged by some of our fine elected officials," Lyon said. "We are confident it is completely legal."

State Sen. Scott McCoy, a Salt Lake City Democrat who is gay, said a court decision on the benefits could be valuable. "This will clarify once and for all ... that there isn't a legal roadblock to offering these benefits," he told The Salt Lake Tribune.

The mayor's order makes Salt Lake City the first government in Utah, one of the nation's most conservative states, to offer domestic partner benefits.

Nationwide, more than 8,000 U.S. employers offer domestic partner benefits, according to the national Human Rights Campaign, which advocates for gay, lesbian, bisexual and transgender rights.