QUESTION: I thought in Cohens v. Virgina the Supreme Court determined that it has the power to review state laws and decisions, and then it reaffirmed its power of judicial review over States idea in Cooper v. Aaron. It seems Michigan v. Long goes agaisnt this idea. Is the diffence that the Long case was based on the state constitution as opposed to just state law?
ANSWER: Not quite. The difference is that the claim in Cohens concerned federal law, not state law. (The distinction between state constitutional law and state statutory law is immaterial for purposes of federal constitutional law.) The Supreme Court of the United States does, indeed, have the authority to review state court decisions (as you point out, and as the Court held in Cohens v. Virgina). But it only can review state court decisions raising the sorts of "cases" and "controversies" listed in Article III, section 2, clause 1. In Michigan v. Long, the only way the case fit within the federal courts' subject matter jurisdiction was if it was a case "arising under this [meaning the federal] Constitution." Thus, if the Michigan Supreme Court's decision rested on adequate and independent state law grounds -- a state constitutional or state statutory provision -- the Supreme Court would have lacked jurisdiction over the case. The crucial point is that the Supreme Court of the United States generally has no power to review the decisions of state courts on questions of state law. On these matters, state courts are the final arbiters.
QUESTION: The Supreme Court can only evaluate state court decisions and state laws that deal with the federal constitution. Is that correct?
ANSWER: Not quite. Look carefully at Article III, section 2, clause 1. That sets out all the cases that Congress can invest in the federal courts -- the ceiling on the federal courts' subject matter jurisdiction. You will notice that it is not just questions concerning federal constitutional law that the Supreme Court can review on appeal from a state court. It can also review cases, most prominently, involving federal statutes or treaties (as well as a number of other types of cases, though Congress has generally only given the Supreme Court appellate jurisdiction from state courts for cases involving federal legal questions).
QUESTION: So if the question is one based on federal law, then that is when the Supreme Court jumps in and can review.
ANSWER: Yes. Or at least it has the power to do so. It only grants certiorari in roughly 0.5 percent of the cases appealed to it.
QUESTION: The Supreme Court cannot challenge state laws, or decisions based on State law?
ANSWER: Those are actually two different questions. The Supreme Court of the United States can review state laws on a claim that the state laws conflict with federal law. But the Court cannot review a claim that a state court's decision is inconsistent with state law. To give an example, the most recent California Supreme Court decision on Prop 8 held that Prop 8 was consistent with the California constitution. That decision was not reviewable by the Supreme Court of the United States. The current case, however, claims that Prop 8 violates the federal constitution. The Supreme Court of the United States would have jurisdiction over the present case even if it were being litigated in state court (which, of course, it is not).
QUESTION: What if a citizen of Michigan wanted to challenge a part of Michigan's constitution as unconstitutional under the federal constitution, or wanted to challenge a Michigan legislative act. Is that appropriate for the Supreme Court to review?
ANSWER: Yes, so long as the claim "arises" under federal law -- that is, the claim is that federal law dictates a different answer. That is "federal question" jurisdiction, and, as discussed above, Article III, section 2, clause 1 expressly provides for this. This was precisely what Martin v. Hunter's Lessee and Cohens v. Virginia allowed.