In an arbitrary and irresponsible decision that will have an enormous impact, not only here in Massachusetts but across the nation, the Supreme Judicial Court (SJC) has decided to change the millenia-old definition of marriage. In Massachusetts, marriage will soon mean “the voluntary union of two persons as spouses, to the exclusion of all others,” thus allowing clerks and registrars to grant marriage licenses to same-sex couples.

The redefinition of marriage as something not tied to sexual complementarity elevates homosexual cohabitation to the same level as marriage. Further, it opens the door to other challenges to the definition of marriage such as incest and polygamy — in effect, fatally wounding the most sacred and valuable institution in society.

After the Nov. 18 decision, homosexual unions have been legally recognized by the SJC, and homosexual unions have been given the legal status and rights belonging to marriage.

In this new scenario, the recent Vatican document on the issue, “Considerations Regarding Proposals To Give Legal Recognition To Unions Between Homosexual Persons,” speaks loudly and unambiguously to Catholics — including Catholic legislators: “Clear and emphatic opposition is a duty. One must refrain from any kind of formal cooperation in the enactment or application of such gravely unjust laws and, as far as possible, from material cooperation on the level of their application. In this area, everyone can exercise the right to conscientious objection.”

Massachusetts and national legislators are scrambling to prepare reactions, solutions or compromises to this ruling. It may be too little, too late. The “wait and see” strategy that politicians have followed for several years has been disastrous. Still, now is the time to act decisively to defend the definition of marriage as a stable relation between a man and a woman.

At the state level, the SJC has mandated that legislators act. Their first action should be a firm vote at the next constitutional convention to approve an amendment to the constitution that would define marriage as the union of a man and a woman. The second step should be to fight for an extension of the 180 day deadline imposed by the court to allow the constitutional process to take place.

At the national level, President Bush has already criticized the ruling, saying it violates the principle that “marriage is a sacred institution between a man and a woman,” and has vowed to work with congressional leaders to defend the sanctity of marriage. House Majority Leader Tom DeLay, R-Texas, has signaled that a constitutional amendment would be a way to “fix” the SJC’s decision that, he says, “has no consideration for the Constitution of the United States.”

Furthermore, the defense of marriage as an institution between a man and a woman will be a defining issue in the 2004 presidential election. A new political reality certainly requires careful consideration of the way Catholics cast their votes. Catholics need to seek out their candidates’ views and positions on crucial issues, such as the definition of marriage. It is imperative that Catholics start thinking beyond traditional party affiliations and consider the issues that matter most.