united-states us-constitution us-supreme-court
What is the theory that allows a state to appeal a judgment of its own supreme court to the US Supreme Court?
<p>Suppose John Doe is facing criminal prosecution in Florida. He raises a 4th Amendment issue, and the Florida Supreme Court grants him relief. At this point, the state of Florida can appeal to the US Supreme Court, and the US Supreme Court can, if it chooses, review the judgment of the Florida Supreme Court.</p>

<p>What puzzles me is this: at this point, there is no federal harm to either party. True, the Florida Supreme Court might have used an erroneous federal constitutional theory to tie the hands of the Florida Attorney General, but nothing in the US Constitution says they can't do that.</p>

<p>What is the justification that prevents this from being considered an abstract question?</p>

<p>The Supremacy Clause.</p>

U.S. Constitution, Article VI, Clause 2:

<blockquote>
  <p>This Constitution, and the Laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and <strong>the judges in every state shall be bound thereby, anything in the constitution or laws of any state to the contrary notwithstanding.</strong> [emphasis mine]</p>
</blockquote>

<p>This is also known as the "Supremacy Clause" of the U.S. Constitution. It prevents any law of any state from acting contrary to the federal constitution. A comment correctly cites multiple cases that use this clause, in part, as the basis for SCOTUS' authority to review State Supreme Court decisions.</p>

<p>So in your hypothetical, the federal issue in play is the clarity of the federal constitution which supersedes state law.</p>

<p>Losing on an interpretation of the federal constitution creates a federal case or controversy.</p>
