One wrinkle worth mentioning: the role of judges on senior status. Federal judges may take "senior status," after they reach age 65, if the sum of their age and their years on the bench is at least 80. (Imagine a judge who was confirmed to the bench at age 50: at 65, he has 15 years of service plus 65 years of life: 80! He's eligible.) Senior status is sort of quasi-retirement. The judge vacates his seat, and the president names a replacement, but can continue, with a reduced case load, to hear cases as part of a three judge appellate panel, or even serve as a federal district judge by designation. He's entitled to maintain an office and hire a clerk. However, he is not part of an en banc court. So it's possible that the three judge panel that delivers an opinion will have been made up of one or more judges that won't sit en banc. More on reddit.com

So I’m assuming you aren’t American. Basically what happens is that the US constitution sets out what Congress can and cannot do. Usually these decisions where a judge finds something to be unconstitutional, it’s a District Court judge. They’re the court of first instance for federal matters. If a district court judge rules something to be unconstitutional, likely other district court judges will look at that ruling as precedent. Sometimes you get two different rulings from two different district courts, and then you need to wait until one of them is heard by the Supreme Court. The Supreme Court is really the final authority on the US constitution. More on reddit.com

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So it's actually incorrect that blocking executive action is a Supreme Court power - it's one that is constitutionally reserved to the lower courts. Let us begin with Article III of the Constitution. The relevant parts say: The judicial power of the United States, shall be vested in one Supreme Court, and in such inferior courts as the Congress may from time to time ordain and establish. ... The judicial power shall extend to all cases, in law and equity, arising under this Constitution, the laws of the United States, and treaties made, or which shall be made, under their authority;--to all cases affecting ambassadors, other public ministers and consuls;--to all cases of admiralty and maritime jurisdiction;--to controversies to which the United States shall be a party;--to controversies between two or more states;--between a state and citizens of another state;--between citizens of different states;--between citizens of the same state claiming lands under grants of different states, and between a state, or the citizens thereof, and foreign states, citizens or subjects. In all cases affecting ambassadors, other public ministers and consuls, and those in which a state shall be party, the Supreme Court shall have original jurisdiction. In all the other cases before mentioned, the Supreme Court shall have appellate jurisdiction, both as to law and fact, with such exceptions, and under such regulations as the Congress shall make. So that's a big block of text, but let's break it down. The Constitution establishes a Supreme Court and instructs Congress to establish "inferior" courts. So it contemplates and anticipates the existence of the lower courts. Importantly, it extends the "judicial power" to both the Supreme Court and the inferior courts. Next, the Article defines the sort of cases which are subject to Federal courts' jurisdiction. One of them is where the US Government is a party. Another is where the US Constitution or laws are the subject. Both of those would be the case in challenging an executive order. So it's definitely in the Federal courts' wheelhouse. The next paragraph is critical to this. It establishes that the Supreme Court has "appellate" jurisdiction. That is, it only hears a tiny class of cases as the first court to hear it, but otherwise hears appeals from lower court rulings. So the structure of the US Courts as defined in Article III means that a case is almost always going to begin its way in the lower courts, and only can wind up at the Supreme Court on appeal. Early in the Republic, in the landmark case, Marbury v. Madison the Supreme Court held a law purporting to allow cases to be brought directly to them as unconstitutional because they only had appellate jurisdiction. The way this ends up working in practice today is that the grunt work of actually enforcing a court order is always done at the district court level. Appeals court rulings generally instruct a lower court on what to do, but then ask the lower court to actually carry it out. So for example here's a somewhat recent court ruling on a jurisdictional question. The last sentence is boilerplate but tells you how the structure of the courts work in most cases: The judgment of the Ninth Circuit is reversed, and the case is remanded for further proceedings consistent with this opinion. So that sentence is sending the case back to the lower court to deal with it based on the principles of law that the Supreme Court laid out. Actually carrying it out is still left to the lower courts. Now, there is something else going on here though with respect to the transgender ban, and also has happened with respect to the travel ban cases, and under the prior administration happened respecting the DAPA program. Normally, a district court would only have jurisdiction over the specific parties to the case in front of it. A circuit court of appeals would only have jurisdiction over the geographic area it covers, and then the Supreme Court has nationwide jurisdiction. So in a suit between two private parties, the district court can only tell those specific parties what to do, the circuit can tell them and any similarly situated parties within the geographic ambit of the circuit, and the Supreme Court can tell everyone what to do. However when one of the two parties is the US Government, things change. The district court telling the parties what to do has effectively nationwide effect, because one of the parties is the government itself, or the responsible officer(s) of the government with nationwide authority. So a nationwide injunction from a district court is unusual in that it can only happen when the government itself is sued. Sometimes that'd be uncontroversial. After the Supreme Court had ruled on a question for example, it might get remanded to the lower court who would be tasked with enforcing that ruling through a nationwide injunction against the government. The issue coming before us today is different in that district courts are issuing injunctions before the higher courts have had a chance to look. This is an article making a case against such nationwide injunctions. More on reddit.com