When reviewing the District Court's assumption of subject matter jurisdiction, does the assumption of diversity of citizenship apply?

When reviewing the district court's assumption of subject matter jurisdiction, we accept its findings of fact unless they are clearly erroneous, while examining questions of law de novo. See McGinty v. New York, 251 F.3d 84, 90 (2d Cir.2001). There are two possible grounds on which the district court's jurisdiction might have been anchored in this case: diversity of citizenship and copyright law. If any of plaintiffs' claims can be based on these jurisdictional grounds, their other claims possibly may be based on supplemental jurisdiction.

I Diversity of Citizenship