And remember that the amnesty action may not be breaking the law. Impeachment/conviction doesn’t need to be for law breaking. McCarthy explains this. It’s a political move, not necessarily legal.
I suspect that it isn't. Even when not written into law, the executive has discretion with regard to enforcement; plus has the pardon power.
And I think the immigration law is written in a way that expressly gives discretion. This tries to be a limited form of discretion, for cases such as "need" and "refugee", etc., which just adds another layer of rhetoric to argue about.
At bottom, this issue is whether Congress or the president sets immigration policy. The fact that there are federal laws on the books makes it appear as though Congress has that role. It will be interesting how far it lets the president step. I predict loud complaints, lawsuits filed by Congress (which will be rejected), and nothing else. Congress has no backbone.