Updated

An assistant Missouri attorney general argued Monday in a St. Louis courtroom that state law, backed by a vote of the people, makes it clear that marriage is defined as between a man and a woman.

But St. Louis City Counselor Winston Calvert countered that the state has no business treating same-sex couples as "second-class citizens."

St. Louis Circuit Judge Rex Burlison is deciding the constitutionality of Missouri's ban on gay marriage. The city of St. Louis issued marriage licenses in June to four same-sex couples, setting up a court fight over the state's 2004 state constitutional amendment banning gay marriage.

It isn't clear when Burlison will rule. St. Louis officials have stopped issuing marriage licenses to gay couples until legal issues are resolved.

Three gay couples watched Monday's hearing. Among them were Bruce Yampolsky, 72, and Terry Garrett, 56, one of the couples granted marriage licenses by the St. Louis Recorder of Deed's office, triggering the legal challenge.

Overturning Missouri's constitutional ban "would at least open doors for the next generation not to have the trials and tribulations that we had," Garrett said after the hearing. "We should be able to decide who we love."

But Assistant Attorney General Jeremiah Morgan told Burlison that Missouri law limits marriage to between a man and a woman. He argued that 71 percent of Missourians voted for that definition of marriage in a 2004 referendum, and the U.S. Supreme Court has time and again allowed states to define marriage.

"It is the state's, and the people's, responsibility to make that decision," Morgan said.

Calvert noted that an increasing number of states are allowing same-sex marriage, including most of the states surrounding Missouri.

"The laws forbid some people from choosing who they marry," Calvert said. "It's only gay and lesbian couples that are treated as second-class citizens by the state."

The hearing was the second in as many weeks involving the question of gay marriage in Missouri. Last week, a hearing took place in Kansas City on a suit filed by 10 couples over the state's failure to recognize same-sex marriages performed in other states. Timing of a ruling in that case also is uncertain.

The lawsuits in Missouri mirror dozens of others across the country that argue state bans on gay marriage violate the due process and equal protection rights of same-sex couples. The suits are based on the same arguments that led the U.S. Supreme Court last year to overturn part of the federal Defense of Marriage Act that denied a range of tax, health and veterans benefits to legally married gay couples.

Nineteen states and the District of Columbia now allow same-sex marriages. The American Civil Liberties Union said it has marriage cases pending against 13 other states, of which five are before federal appeals courts.