BOSTON (AP) – The same court that made Massachusetts the first state to legalize same-sex marriage ruled July 10 that a proposed constitutional amendment to ban future same-sex marriages can be placed on the ballot, if approved by the Legislature.

The ruling was in a lawsuit brought by gay rights supporters who argued that Attorney General Tom Reilly was wrong to approve the ballot measure because they said the state constitution bars any citizen-initiated amendment that seeks to reverse a judicial ruling.

In a unanimous decision, the Supreme Judicial Court said the proposed amendment is not a “reversal” of the court’s ruling legalizing same-sex marriage but a proposed change to the state constitution, which can be legally done through a citizen initiative.

“The underlying substantive law is simply changed to reflect the present intentions of the people, and that new law will be applied thereafter in any subsequent case or cases,” the court said in its ruling.

Justice John M. Greaney, in a concurring opinion, warned that approving an amendment banning same-sex marriage would be discriminatory because it would remove the rights of same-sex couples to the legal, social and financial benefits of marriage.

“The only effect of a positive vote will be to make same-sex couples, and their families, unequal to everyone else; this is discrimination in its rawest form,” Greaney wrote.

With a landmark 2003 ruling, the court cleared the way for same-sex marriages to begin in Massachusetts in May 2004. More than 8,000 same-sex couples have married since.

The state Legislature is expected to take up the ballot question this week during a constitutional convention.

Citizen-initiated ballot questions must be certified by the attorney general and then approved by two consecutive legislative sessions. Before the marriage question could be placed on the 2008 ballot, supporters would need to win the votes of 50 lawmakers – 25 percent of the Legislature – in two consecutive sessions.

Lee Swislow, executive director of Gay & Lesbian Advocates & Defenders – which filed the lawsuit in January – said she was disappointed but knew it would be an uphill battle. She said the fight is not over.

Massachusetts is the only state that allows same-sex marriage, although Vermont and Connecticut allow same-sex civil unions that confer the same legal rights as heterosexual married couples.

Supporters of a constitutional amendment in Massachusetts predict they will have enough votes to win the first round of approval from the Legislature. They would also need to win approval in the next legislative session.