Do civil servants have trade unions in the US? This seems like a place they could step up to offer advice.
Yes, and they have sued over several events so far. I don’t know what advice they could give in the moment.
If I were in their shoes I would take some small comfort from a constitutional lawyer even saying "officially we don't know".
It's not often you're asked to do something that could break the law, with the whistle-blowing chain being potentially broken at the top.