Wouldn't that be grounds for the easiest appeal ever?
It should be because under Rule 65, which is what you have to follow to get a TRO, the movant (the states here) has to certify that they had good reason to not provide notice to the non-movant (the US here). This is usually for emergency rulings on a short notice where irreparable harm has to be avoided.
For example, if there's a protest encampment going on where the municipal authority is trying in the middle of the night to unlawfully bulldoze the protestor camp and break them up, the protestors could seek a TRO at an odd hour from a judge saying "We have this immediate problem occurring where if we don't act immediately, there will be irreparable harm in the form of bulldozing our protest and breaking it up without due process of law. We tried to contact the city but it's the middle of the night and we can't wait for them to show up, because by that time it will be too late. Please freeze the situation so nothing is irreparably harmed, and then we can have a hearing with all the parties to determine whether this can proceed ASAP."
That's not what's happening here. The purported unlawful conduct has already been occurring, and the opposing party is extremely available to respond immediately. It would be hard to find a party that is more available to respond than the United States, whose lawyers (the US Attorney) are stationed right next door to the judge. The action being stopped is also not so obviously wrong that it has to be stopped. And there are questions about whether an injunction is proper given that the harm has already occurred to some extent. There are also questions about whether the states have standing and whether the complaint states claims that could pass a Rule 12(b)(6) motion to dismiss or Rule 56 motion for summary judgment (which is relevant to the preliminary injunction standards, which this should have been treated as a motion for). And there are questions about whether this is even a justiciable controversy—meaning that there are certain controversies involving the political process and executive/legislative branches that courts don't involve themselves in because they are part of the political process and not amenable to judicial interference.
Part of the problem is that the ruling, as far as I can tell, was from the bench. Given the extreme disruption which this TRO aims to cause to the functioning of the executive branch, there are huge questions about constitutionality and justiciability that need to be addressed in some form so that the ruling is memorialized for effective appellate review. That did not occur here at all. That's really bad, because there needs to be something exhibiting the reasoning of the court so that it can be determined on appeal whether the ruling was proper or not. The absence of any written reasoning makes this look like an attempt to insulate the ruling from effective appellate review, which is
extremely improper.
For contrast, the judge that initially blocked the birthright citizenship executive order said from the bench that constitutional precedent stands against what the US government was trying to do. You may disagree with whether the constitutionality is improper, but it at least referred to a reason for the order. And that can be reviewed on appeal in the sense that a court could go look de novo at the interpretation of the Constitution and the cases which form the basis for birthright citizenship to determine whether the judge's ruling was proper.
I can't stress how extremely improper this ruling on the Treasury is. Both on the merits and procedurally, it's fraught with impropriety. Part of the rule of law is not just obeying the judicial review powers of the judiciary, but also the judiciary acting carefully to make sure its rulings are properly explained, procedurally proper, and cautiously drawn to not go further than necessary in interfering with the conduct of the parties. A court should
never issue an unreasoned ruling of this magnitude without the basic buy-in of the non-moving party to the process that resulted in the ruling. Judges should not be pushing parties to the edge of reason and daring them to disobey, especially when it could appear to be for political reasons. That's part of our separation of powers and the character of our Article III judiciary. Otherwise, you breed disrespect for the courts. And when nobody believes in the power of judicial resolution anymore, the natural result is to go back to ye olden days of early Anglo-Saxon resolution of disputes (which is what happens in the third world and tribal societies all the time), i.e. killing each other.