Why did the Court rule on injunction scope?

In Trump v. Casa the Supreme Court ruled that district judges cannot issue "universal injunctions" against the federal government… Well, what the hell does that mean? The ruling comes in regard to Trump's executive order on birthright citizenship. Is the Trump administration accurately "rediscovering" the true meaning of the Constitution, or just twisting and mangling it to make sure nobody here illegally can confer citizenship on their kids? Tim Sandefur of the Goldwater Institute joins to discuss.