Company ending remote work with 2 weeks notice - is this legal?

I've been working fully remote for a tech company for 3 years. Was hired as remote from day one. Today they announced that everyone needs to be in the office 5 days a week starting Dec 17th (2 weeks from now).

I live in Austin and the office is in San Francisco. They're saying I either relocate or resign. No severance mentioned.

Can they really just change the terms like this with two weeks notice? Don't I have any recourse here?

Update: About 15 of us sent a joint email to leadership asking for 90 days notice and either relocation packages or severance. We'll see what happens.

Really appreciate all the advice here. Even if they don't budge, at least I know my options now. And I'm definitely not resigning - if they want me gone, they can terminate me.