Again, if difficulties arise in the levying of import duties which have been voted by Congress, the Federal court must decide the case, because it arises under the interpretation of a law of the United States.
This rule is in perfect accordance with the fundamental principles of the Federal Constitution.

The Union, as it was established in 1789, possesses, it is true, a limited supremacy; but it was intended that within its limits it should form one and the same people.

*h Within those limits the Union is sovereign.

When this point is established and admitted, the inference is easy; for if it be acknowledged that the United States constitute one and the same people within the bounds prescribed by their Constitution, it is impossible to refuse them the rights which belong to other nations.

But it has been allowed, from the origin of society, that every nation has the right of deciding by its own courts those questions which concern the execution of its own laws.
To this it is answered that the Union is in so singular a position that in relation to some matters it constitutes a people, and that in relation to all the rest it is a nonentity.