When the American Civil Liberties Union contacted Michael Scott in 2013 about bringing a pro bono case for a newly engaged gay couple, he knew national attention would follow.

His 39-lawyer firm, Hillis Clark Martin & Peterson in Seattle, hadn’t even filed the complaint when the Washington state attorney general’s office brought a highly publicized case of its own. And the defendant, a 70-year-old local florist, had retained Alliance Defending Free­dom, an amply funded conservative Christian organization focused on cases involving religious freedom.