However, because litigants can (and often do) raise federal claims in state courts, many cases are not so simple, and this general rule breaks down.
The adequate and independent state ground doctrine provides certain exceptions to this general rule and guides the U.S. Supreme Court’s exercise of jurisdiction over these complex cases.
See Michigan v. Long, 463 U.S. 1032, 1038 (1983) (“It is, of course, incumbent upon this Court to ascertain for itself whether the asserted non-federal ground independently and adequately supports the judgment.” (internal quotation marks omitted)); Fox Film Corp. v. Muller, 296 U.S. 207, 210 (1935) (“[W]here the judgment of a state court rests upon two grounds, one of which is federal and the other non-federal in character, our jurisdiction fails if the non-federal ground is independent of the federal ground and adequate to support the judgment.”); Murdock v. City of Memphis, ("[W]hether there exist other matters in the record actually decided by the State court which are sufficient to maintain the judgment of that court, notwithstanding the error in deciding the Federal question.
Antecedent state-law grounds (i.e., state rules of procedure) are adequate to support a judgment unless they (1) are arbitrary, unforeseen, or otherwise deprive the litigant of a reasonable opportunity to be heard, see, e.g., Staub v. City of Baxley, 355 U.S. 313, 319-20 (1958), or (2) impose an undue burden on the ability of litigants to protect their federal rights, see, e.g., Felder v. Casey, 487 U.S. 131, 138 (1988).
If it is not "apparent from the four corners” of the opinion that the judgment rests on an independent state law rule, then, unless it is “necessary or desirable” to obtain clarification from the state court itself, the Supreme Court will presume that the decision rested in part on federal law, thereby rendering it reviewable.