Maritime law is mostly like the rest of common law, but there are some fun quirks here and there. One of those is 28 U.S.C. § 1292(a)(3), which provides:
Interlocutory decrees of such district courts or the judges thereof determining the rights and liabilities of the parties to admiralty cases in which appeals from final decrees are allowed.
Ordinarily, with some important exceptions, a case has to be over before you can appeal in federal court. 1292(a)(3) provides an exception for admiralty causes of action too. But how broad is it? To answer that, you have to answer another question: how do we interpret statutes? Going by the plain language, you'd think it's any judgment that determines the rights and liabilities of the parties - i.e. all of them. But if you look at purpose, it's much narrower than that - the original idea is that often a special master will determine liability and damages are determined by separate process, and the goal is to allow appeal of the former before the latter is determined.
So we find the dilemma in SCF Waxler Marine LLC v. ARIS T (5th Cir. 2018). Judge Zainey had ruled that an insurance carrier was allowed to limit its liability along with its insured if its insured won limitation.* However you want to call it, this is something that determines some of the rights and liabilities of the parties, but it isn't a final adjudication of much of anything except that narrow issue. The other side appealed. The Fifth Circuit said "no right of appeal." 1292(a)(3) appeals are only for final adjudication of an entire part of a claim. "We have clarified that appellate jurisdiction is generally appropriate whenever an order in an admiralty case dismisses a claim for relief on the merits," says the Court. If one plaintiff is dismissed, there's a final adjudication, for instance. If the insurer had been dismissed (say, on the argument it didn't provide coverage at all), same thing. No need to wait for the entire case to be over. But finding that the insurer is entitled to make an argument to limit its liability? Not so much.
There is pretty significant case law on this, so the decision is not really a surprise and the appeal was a long shot.
*Louisiana allows the insurer to be named directly. The limitation of liability act allows the vessel owner to limit its liability to the value of the vessel + freight at the end of the voyage if the accident did not involve its privity or knowledge. The vessel's insurer can only avail itself of limitation if it has a Crown-Zellerbach clause. Whether this policy's language met the Crown Zellerbach question was the underlying question. The district court said "yes."