Those who argued against a new state constitutional amendment banning same-sex marriage say its potential impact on a bigamy conviction appeal is just the latest example of the measure having a broader impact than just defining marriage.

Utah Supreme Court Chief Justice Christine Durham on Thursday, during a hearing on the appeal, questioned whether Amendment 3 would prevent the state from establishing co-habitation as a means of prosecuting bigamy.

The amendment defines marriage as the relationship between "a man and a woman" and prevents giving legal recognition to any other "domestic union."

In an interview after the hearing, Monte Stewart, president of the Marriage Law Foundation and a prosecutor of polygamist Tom Greene, said Amendment 3 shouldn't impact Rodney Holm's appeal of a bigamy conviction for taking his 16-year-old sister in law as a third "spiritual" wife.

That's because Amendment 3 prevents the state from giving legal recognition to, or sanctioning, a bigamous relationship, he said. It does not, Stewart said, prevent the state from establishing whether a bigamous relationship exists for the purposes of prosecution.

"The state is hardly approving the second relationship when it throws you in the slammer for being part of it," he said.

However, Supreme Court justices questioned Thursday how the state can prosecute bigamy if a person is not legally married to more than one person at the same time. Holm, who is married to his first of three wives, does not claim to be legally married to his other two "spiritual" wives.

Justices questioned whether living with someone can be crime and noted the bigamy statute is intended to prevent, when a married person marries again without the other spouse knowing.

Equality Utah Vice Chairman Scott McCoy said he's not surprised that Amendment 3 would be brought up in a bigamy case. During the Amendment 3 campaign, Tapestry Against Polygamy had raised concerns that the marriage amendment could hamper efforts to prosecute polygamists.

"If you say no other domestic union may be recognized as a marriage or be considered a marriage . . . now, how do you characterize the other domestic union that characterizes a polygamist relationship?" McCoy asked.

McCoy said it's just the latest example of the marriage amendment being used in ways for which it wasn't intended.

A Salt Lake attorney has filed a motion for a male client who contends that Amendment 3 makes it unconstitutional to enforce a court protective order that his former live-in girlfriend got from a judge.

"I think we'll continue to see it used in these ways," McCoy said. "Soon, we'll see (court) decisions coming down."