In a Habeas class action seeking relief for immigration detainees in the current pandemic, supervisory Mandamus doesn't run because the lower court has not palpably erred; it has reduced the detainee population significantly. Advisory Mandamus doesn't run, since the determination of pandemic severity is a factual question, not a legal question, and since the population has been lowered, the balance between extraordinary circumstances and likely success doesn't need to be corrected.