The Third Circuit heard oral argument on March 11 in a challenge to Delaware's ban on so-called "assault weapons" and ammunition magazines that hold over 17 rounds. Three overlapping cases were consolidated for argument on appeal from the denial of a preliminary injunction. Before the Court got into the meat of the Second Amendment dispute, Judge Stephanos Bibas raised a question about the preliminary injunction standard as it applies in Second Amendment cases: do the plaintiffs need to show that every preliminary injunction factor weighs in their favor, or is it enough to show they are likely to succeed on the merits?
The Supreme Court refers to the preliminary injunction as "an extraordinary remedy" that requires plaintiffs to make a "clear showing" on four factors before being granted: (1) likelihood of success on the merits, (2) that they face irreparable harm in the absence of an injunction, (3) that the balance of the equities favor them, and (4) that the public interest would be served by the injunction. The plaintiffs in Delaware focused on the first point—that they were likely to show the laws they challenged violate their Second Amendment rights. Judge Bibas questioned whether that was enough.
It should be. In fact, while there are putatively four factors to be considered in granting a preliminary injunction, in litigation against the government over the constitutionality of a law, in practice they tend to collapse. In such cases, "likelihood of success" is "the first among equals" and is typically dispositive, L.W. by & through Williams v. Skrmetti (6th Cir. 2023), and the third and the fourth factors, the public interest and the balance of the equities are considered as one. Nken v. Holder (U.S. 2009). Furthermore, if plaintiffs show that the law they challenge violates the Constitution, then those final factors necessarily weigh in their favor, because "the enforcement of an unconstitutional law vindicates no public interest." K.A. ex rel. Ayers v. Pocono Mountain School District (3d Cir. 2013).
