The federal supplemental jurisdiction statute, 28 U.S.C. § 1367, allows a litigant with a federal claim to bring into federal court with it any state claims that are so related to the federal claim that they “form part of the same case or controversy under Article III of the United States Constitution.”  Thus, a plaintiff seeking damages under 42 U.S.C. § 1983 for violation of her 4th Amendment rights could litigate in the same federal-court action any state-law claims (like violation of the state constitution, false arrest, assault and battery) arising out of the same incident. Or a plaintiff seeking damages for a racially discriminatory job termination, under Title VII of the 1964 Civil Rights Act, could also litigate his state-law discrimination or breach-of-contract claims in the same action in federal court.
But what happens when the federal claims are dismissed without resolving the state claims? Can the plaintiff refile the state claims in state court, and how long does he or she have to do so?

Section 1367(d) says that the “period of limitations . . . shall be tolled while the claim is pending [in federal court] and for a period of 30 days after it is dismissed unless State law provides for a longer tolling period.” The Supreme Court today, in Artis v. District of Columbia, resolved a split among lower courts about what this statutory language means, against the backdrop of a case in which the plaintiff filed her case in federal court while there was still nearly two years left of the three-limitation period on her state-law claims (D.C. is a “state” for purposes of the statute). Her federal claim took 2-1/2 years to resolve. After the federal court dismissed it, she waited 59 days to refile in the local courts, which ruled that she had waited too long, because, though “tolled,” the local statute of limitations expired while the action was in federal court, so that she had only the 30-day statutory “grace” period in which to refile.
In a 5-4 decision written by Justice Ginsburg (joined by the Chief Justice and Justices Breyer, Sotomayor, and Kagan), the Court held that when the local statute of limitations was “tolled” by the federal filing, the clock stopped running, so once the case was dismissed time began to run again, and she had the nearly two years that were left when she filed her federal case in which to refile her state-law claims. Justice Gorsuch, joined by Justices Kennedy, Thomas, and Alito, dissented.