The law stops short of allowing homosexual couples to marry, the Seattle Times reported. But it adds domestic partners to every state benefit, right or entitlement extended to married couples.
Gregoire signed the package of three bills Monday in a ceremony attended by several hundred people, most of them same-sex couples. The bills take effect July 26.
The legislation applies to homosexual couples and to heterosexual couples registered as domestic partners when one member of the partnership is at least 62.
A coalition of religious conservatives, Protect Marriage Washington, plans to campaign for a referendum in November aimed at appealing the law. Another group, Decline 2 Sign, is raising money for an effort to keep the issue off the ballot.