“[T]he notion of ‘comity,’ ” Justice Black asserted, is composed of “a proper respect for state functions, a recognition of the fact that the entire country is made up of a Union of separate state governments, and a continuance of the belief that the National Government will fare best if the States and their institutions are left free to perform their separate functions in their separate ways. This, perhaps for lack of a better and clearer way to describe it, is referred to by many as ‘Our Federalism’. . . .”1331 Comity is a self-imposed rule of judicial restraint whereby independent tribunals of concurrent or coordinate jurisdiction act to moderate the stresses of coexistence and to avoid collisions of authority. It is not a rule of law but “one of practice, convenience, and expediency,”1332 which persuades but does not command.
- Younger v. Harris, 401 U.S. 37, 44 (1971). Compare Fair Assessment in Real Estate Ass’n v. McNary, 454 U.S. 100 (1981), with id. at 119–25 (Justice Brennan concurring, joined by three other Justices).
- Mast, Foos & Co. v. Stover Manufacturing Co., 177 U.S. 458, 488 (1900). Recent decisions emphasize comity as the primary reason for restraint in federal court actions tending to interfere with state courts. E.g., O’Shea v. Littleton, 414 U.S. 488, 499–504 (1974); Huffman v. Pursue, Ltd., 420 U.S. 592, 599–603 (1975); Trainor v. Hernandez, 431 U.S. 434, 441 (1977); Moore v. Sims, 442 U.S. 415, 430 (1979). The Court has also cited comity as a reason to restrict access to federal habeas corpus. Francis v. Henderson, 425 U.S. 536, 541 and n.31 (1976); Wainwright v. Sykes, 433 U.S. 72, 83, 88, 90 (1977); Engle v. Isaac, 456 U.S. 107, 128–29 (1982). See also Rosewell v. LaSalle National Bank, 450 U.S. 503 (1981); Fair Assessment in Real Estate Ass’n v. McNary, 454 U.S. 100 (1981) (comity limits federal court interference with state tax systems); Levin v. Commerce Energy, Inc., 560 U.S. ___, No. 09–223, slip op. (2010) (comity has particular force in cases challenging constitutionality of state taxation of commercial activities). And see Missouri v. Jenkins, 495 U.S. 33 (1990).