This clearly fell into the realm of admiralty law, which is part of the federal judicial power according to Article III of the Constitution.
Yet the judges of the Florida Territorial Court had four-year terms, not the lifetime appointments required by Article III of the Constitution.
Marshall's solution was to declare that territorial courts were established under Article I of the constitution.
As such, they could not exercise the federal judicial power, and therefore the law that placed admiralty cases in their jurisdiction was unconstitutional.
The argument that mere statutory tenure is sufficient for judges of Article III courts was authoritatively answered in Ex parte Bakelite Corp.:[1]