7. When Congress enacts a federal statute, the presumption is that both the federal and the state courts have competence to enforce the law. This presumption of concurrent jurisdiction is rooted in a “system of dual sovereignty”:

This deeply rooted presumption in favor of concurrent state court jurisdiction is, of course, rebutted if Congress affirmatively ousts the state courts of jurisdiction over a particular claim. * * * Thus, the presumption of concurrent jurisdiction can be rebutted by an explicit statutory directive, by unmistakable implication from legislative history, or by a clear incompatibility between state-court jurisdiction and federal interests. * * *