A constitutional ban on equal marriage in the US state of Texas is being challenged by two couples in a San Antonio federal court.

Arguments could be heard as soon as January in the case, as it progresses.

Lawyers acting on behalf of the couples argued that the ban violates the couples’ right to enjoy the legal benefits of marriage. Citing the US Supreme Court decision to strike down the Defense of Marriage Act, they argued that such a ban violates the federal constitution.

The state’s attorney general Greg Abbott, has said he will defend the law.

A constitutional amendment was made in 2005, when voted on by Texans, which excluded same-sex couples from the definition of marriage.

Two couples who had married in Massachusetts were granted divorces in Texas, however the state Attorney General Greg Abbott, who is now in the running to become Governor, intervened earlier this month. A separate lawsuit is taking place currently.