They’re not using the double jeopardy clause in the US constitution, because, as you stated, the case law on that doesn’t protect him from dual state and federal prosecution.
Instead, Mr. Mangione is moving to dismiss the state case on the basis of New York’s separate double jeopardy law. That law binds the state of New York, and prevents them from prosecuting something that has already been jeopardised at the federal level.
They’re not using the double jeopardy clause in the US constitution, because, as you stated, the case law on that doesn’t protect him from dual state and federal prosecution.
Instead, Mr. Mangione is moving to dismiss the state case on the basis of New York’s separate double jeopardy law. That law binds the state of New York, and prevents them from prosecuting something that has already been jeopardised at the federal level.