Many immigration and border requirements are clearly spelled out in law. Laws the administration is enforcing as written. Like many other issues, Congressional Republicans have chosen not to update these at any point over the last couple decades, while also complaining about border issues, simply so they can blame any Democrat President.

This isn't a new issue. It's an issue the Republicans clearly plan. As soon as a Republican is in the White House the "imminent" border issues disappear, or the President enacts some over the top fascist solution that doesn't actually do anything for the cause. And Congress then ignores the causes again so they can complain when the Democrats inevitably regain control and are stuck spending time fixing the fuck ups instead of handling the actual causes.