Parishes in the Archdiocese of Seattle are free to participate in gathering signatures for a referendum challenging a Washington state law that legalized same-sex marriage.

Seattle Archbishop Peter Sartain, who testified against the measure when it was still under consideration by the Legislature, had asked parishes not to collect signatures on Palm Sunday or Easter Sunday.

He is opposed to changing the legal definition of marriage and his approval of signature gathering in parishes for Referendum 74 gives voters the option to reject the measure passed in February by the state Legislature and signed by Gov. Chris Gregoire, a Catholic.

Opponents of legalizing same-sex marriage have until June 6 to gather 121,577 signatures to suspend the law until the public makes a decision about it on Election Day in November. Otherwise the law takes effect June 7.

While voters in five states this year will decide the fate of ballot measures dealing with marriage, Washington is one of only two states where a public vote will determine whether same-sex marriage is legalized. The other state is Maryland, where in February lawmakers passed a bill to legalize such marriages and in March it was signed by Gov. Martin O’Malley, who also is a Catholic.

The Maryland law will go into effect in January 2013 unless voters reject it in November. To put a referendum to repeal it on the ballot, its opponents must gather nearly 56,000 signatures.

New York, Connecticut, Massachusetts, Iowa, Vermont, New Hampshire and Washington, D.C., allow same-sex marriages. Along with Washington state and Maryland, California also has a same-sex marriage law that has not taken effect because of legal challenges.