Supporters and opponents of the statewide legalization of same-sex marriages are rallying their troops today, the final day briefs concerning civil unions as an alternative to civil marriages will be accepted by the Massachusetts Supreme Judicial Court.

The state Senate, backed by opponents of the ruling, asked the SJC to consider a bill calling for civil unions instead of civil marriages. Civil unions allow couples fewer financial and social security benefits than civil marriages, but still recognize couples as joined.

Daniel Avila, associate director of policy and research for the Massachusetts Catholic Conference, said civil unions would be positive for both gay couples and those who believe in marriage as a union between a man and a woman.

“The civil unions bill … says partners will be treated in all respects as spouses, but not in a marriage,” Avila said.

Despite the differences between civil marriages and civil unions, Avila claims the civil unions bill is much like the civil marriages bill.

“The bill itself is a marriage bill,” Avila said. “The language in the bill that says ‘marriage’ will be considered both civil union and marriage.”

Still, supporters of the gay marriage ruling believe civil unions are not enough for gay couples.

“This was a civil rights issue,” said Bonnie Sashin, communications director of the Boston Bar Association, which supports the ruling. “It is discriminatory to deny same-sex couples of their civil rights.”

Testifying before the state legislative committee on the judiciary, BBA President Renee Landers said civil marriages are special social distinctions that present many benefits for couples.

“Withholding the law’s recognition of the marriage commitment from same-sex couples harms these couples, their children and their families, and creates a disparity that belies the promise of liberty and equal protection of the laws established under the Massachusetts and United States constitutions,” Landers said.

On Feb. 11, a joint session of the Massachusetts House and Senate is scheduled to vote on an amendment to define marriage as a union between a man and a woman. If a majority of legislators approves the amendment in two separate sessions, Massachusetts voters will then decide in a referendum whether to pass the ban on same-sex marriages. The amendment could not be passed until 2006 at the earliest.

Opponents of the ruling say it is vulnerable because the SJC ruled before any legislative action. Evelyn Reilly, director of public policy for the Massachusetts Family Institute, said the wheels are in motion to overturn the decision.

“We have primary sponsors to a constitutional amendment for marriage as a union between a man and a woman,” Reilly said. “The SJC did not follow their own constitutional procedures.”

Avila said the SJC’s ruling may have been due to behind-the-scenes lobbying.

“There is a rumor that there is a reluctant, forced member of the SJC who joined the majority at the last moment for a price,” Avila said. “The price [of the lobbying] was a majority opinion and to give the Legislature 180 days to do something [to prevent the ruling].”

Avila said a constitutional amendment would let the voters decide the legitimacy of the ruling.

“The constitution of our state refers to the state having co-equal branches,” Avila said. “The Legislature directly represents a consensus of the people. The people should debate and decide whether a ruling should stand,” he added, “and it would reaffirm marriage as defined between a man and a woman.”

The legislative vote on Feb. 11 is the second of three important dates for the ruling. May 11 is the day the November ruling goes into effect, allowing gay couples to get married.

“We’re sort of looking at pictures of a horizon in Iraq,” Avila said. “We’re looking for the bombs to burst.”

Avila was among the opponents of the ruling who rallied with the newly formed Coalition for Marriage at the Massachusetts Statehouse last Wednesday.

“We have an uphill battle,” Avila said. “We are pleased with this grassroots movement.

“The more information about what the SJC did gets out there, the more people are getting upset,” Avila said. “It’s the same on the national level. Various polls are being released that support for same sex marriage is plummeting.”

Last Thursday, supporters of the ruling countered with a rally at the Statehouse. BBA President-elect M. Ellen Carpenter told the crowd civil marriage for gays is the only constitutional answer, according to a press release from the BBA.

“People are free to say they don’t like this decision,” Carpenter said. “But there’s no ambiguity about what is constitutionally required by the court’s decision: same sex couples must be granted marriage licenses.”