How have we dealt with the issue of federal subject matter jurisdiction?

Since we are obliged to satisfy ourselves that jurisdiction exists, Oneida Indian Nation v. New York, 860 F.2d 1145, 1151 (2d Cir.1988), cert. denied, 493 U.S. 871, 110 S.Ct. 200, 107 L.Ed.2d 154 (1989), at oral argument we asked the parties to submit letters briefing jurisdiction. The Domestic Reinsurers now argue that marine reinsurance contracts are not subject to admiralty jurisdiction, that diversity jurisdiction was defeated by the naming of foreign entities as plaintiffs and as defendants, and that there is therefore no federal subject matter jurisdiction whatsoever.