court to consider whether to apply regional circuit law or Federal Circuit law to particular issues presented. In many cases, the choice is not critical, given the uniformity of federal jurisprudence governing much of the law. But for some issues, there are meaningful differences that require us to decide which law governs.
Here, we are called upon to decide between Federal Circuit and Third Circuit law on threshold issues affecting our jurisdiction over this appeal. As noted above, this is an appeal by Chiron from the grant by the Delaware district court of Lab-Corp’s motion to enjoin Chiron’s prosecution of the parallel action filed by Chiron in California four hours after the Delaware action. For clarity, when we speak of “parallel actions,” we are referring to co-pending patent infringement and declaratory judgment actions involving the same patents and the same parties. Chiron contends that Federal Circuit law governs and that under the law of this circuit, the grant of an injunction against a parallel action is immediately appealable under 28 U.S.C. § 1292(a)(1). LabCorp counters that regional circuit law governs and that under the law of the Third Circuit, the grant of the motion to enjoin the parallel action is interlocutory, is reviewable only by petition for writ of mandamus, and is not ripe for appellate review.
1. Applicable Law
Section 1292(a)(1) provides:
[T]he courts of appeals shall have jurisdiction of appeals from ... Interlocutory orders of the district courts of the United States ... granting, continuing, modifying, refusing or dissolving injunctions, or refusing to dissolve or modify injunctions ....
28 U.S.C. § 1292(a)(1) (2000).
Although the plain language of the statute appears to be both unambiguous and compelling, there is a circuit split concerning whether injunctions' enjoining co-pending actions in other courts are appealable under 28 U.S.C. § 1292(a)(1). See 19 James Wm. Moore et al., Moore’s Federal Practice § 203.10[6][b][i], at 203-38 & n. 85 (Matthew Bender 3d ed. 2004) (“Moore’s Federal Practice”); HBE Leasing Corp. v. Frank, 48 F.3d 623, 632 n. 6 (2d Cir.1995) (observing the circuit split). Several courts of appeals, including this court and the Second, Fifth, and Tenth Circuits, have concluded that injunctions against co-pending litigation in other district courts are appealable under section 1292(a)(1). See, e.g., Katz v. Lear Siegler, Inc., 909 F.2d 1459, 1461. (Fed.Cir.1990) (“[T]he grant of an injunction against continuing suit in another forum is appealable as of right, 28 U.S.C. § 1292(a)....”); Klein v. Adams & Peck, 436 F.2d 337, 339 (2d Cir.1971) (“Because [the . district courtj’s directive is an injunction- which unconditionally bars plaintiff from proceeding in his other actions, that order is a decision from which appeal may be taken.”); Phillips v. Chas. Schreiner Bank, 894 F.2d 127, 130 (5th Cir.1990) (“[TJhis circuit has long recognized a clean distinction between injunctions- prohibiting proceedings in other courts, which are appeal-able, and orders, whether or not styled ‘injunctions,’ that control proceedings only in the court that issues the order. Thus, if a district court acts to halt proceedings in another court, its action is indeed an injunction within the meaning of section 1292(a)(1) .... ” (internal citation, brackets, and quotation marks omitted)); MAI Basic Four, Inc. v. Basis, Inc., 962 F.2d 978, 981 (10th Cir.1992) (“Since [Baltimore Contractors v. Bodinger, 348 U.S. 176, 75 S.Ct. 249, 99 L.Ed. 233 (1955)], the courts of appeals have generally adopted a per se rule for dealing with orders like the in