Veteran King County Superior Court Judge Mary Yu is the newest member of the Washington State Supreme Court, the first Asian-American and the first gay member of the high court.

Yu was appointed by Gov. Jay Inslee to replace retiring Justice Jim Johnson, a conservative defender of property rights who once joined in a majority ruling against gay marriage.

“Her appointment today is a moment that all Washingtonians can be proud of,” Inslee said.

Yu is best known for having performed the state’s first same-sex marriage at 12:01 a.m. in December 2012 when marriage equality took effect in Washington State. She spent seven hours in black robes pronouncing vows that day.

Yu was also the judge who pronounced wedding vows for King County Executive Dow Constantine and longtime partner Shirley Carlson on Halloween of last year.

Yu comes to the high court with a varied background. She has a graduate degree in theology from Mundelein of Loyola University in Chicago. She is a onetime director of the Office of Peace and Justice of the Catholic Archdiocese of Chicago. She is a graduate of the University of Notre Dame Law School.

Yu was named to the King County Superior Court bench in 2000 by Gov. Gary Locke. She has collected such honors as a Municipal League Foundation “Public Official of the Year” award, and the Norm Maleng Award of the Washington State Bar Association. She worked as deputy chief of staff for the late King County Prosecutor.

In accepting appointment on Thursday, Yu chose to praise the role played by the state’s trial courts in forwarding the rule of law. She pledged to “work collaboratively” with colleagues.

“Trial court judges, at every level of the court, are the work horses of our system of justice,” Yu said. “I am proud to come from their ranks and will do all that I can to remember that a trial court remains the place where the law is actually applied to everyday life.”

One colleague went out of his way to praise Yu’s appointment. “I am so happy for Washington,” Justice Steve Gonzalez, a former King County Superior Court colleague, wrote on his Facebook page.

Justice Johnson was a sometimes prickly voice from the right, taking his colleagues to task when they asked the Legislature for a timetable on implementing the McCleary decision, which requires full funding of the state’s K-12 schools.

Before coming onto the court nine years ago, Johnson served as a legal adviser to Tim Eyman on the former Mukilteo watch salesman’s multiple initiatives.

Justice Yu, in 2003, wrote a decision that overturned as unconstitutional the Eyman-sponsored Initiative 776, which both set $30 car tab fees and sought to bring about a re-vote on Sound Transit’s light rail program.

“By tying the proposals together,” wrote Judge Yu, “I-776 forced voters into a Hobson’s Choice of having to vote for both or against both. The practical effect is that . . . this initiative was able to combine the votes of voters who favored $30 tab fees with the votes of whose who opposed Sound Transit’s light rail program.”

Yu read a portion of her ruling from the bench that appeared to rebuke both Eyman and his lawyers, saying:

“A bedrock principle of American democracy is that our laws must comply with the Constitution, whether that law was enacted by the Legislature or directly by the people through an initiative process.”

Reflecting on the Johnson-to-Yu transition, Andrew Villeneuve of the Northwest Progressive Institute joked: “I cannot see this as a happy day for Tim Eyman.”

Justice Yu must run for election this fall.