Anyone on here friends with a UW-alum or Seattle-area lawyer who might be interested but doesn’t read HN?
It's very common in the UK. The most visible part of the unions is running social activities, often bars and events, but they can also provide legal advice to their members.
Graduate students sometimes are part of unions, but usually only if they're also employed by the university (somebody paying full tuition for an MBA probably isn't in a union, but a doctoral student teaching or doing research might be).
Undergrads doing part-time work at the university to pay bills (dining hall, bookstore, etc) could be, in theory, but probably aren't.