but confusion and contradiction could arise?

2. To settle disputes between the States and citizens of different
States.

3. To construe and interpret the Constitution itself, and decide all
disputes arising under it act of either Congress or of a State
legislature contrary to the Constitution can therefore be valid. Hence,
the necessity of some power which should have authority to determine the
constitutionality of an act when brought into question, and--

5. There should be the power of determining the constitutionality of any
act of a State legislature, and thus enforce upon State legislatures the
restrictions laid upon them, such as, for example, the inability to lay
impost duties, to pass laws violating the obligation of contracts, etc.,
or to regulate objects given exclusively to Congress. The manifest
necessity of such a power may be best stated by using Hamilton's own
words (Federalist, 30):

"What would avail restrictions on the authority of the State
legislatures without some constitutional mode of enforcing the
observance of them? The States, by the plan of the Constitution, are
prohibited from doing a variety of things, some of which are
incompatible with the interests of the Union; others with the principles
of good government. The imposition of duties on imported articles, and
the emission of paper money are specimens of this kind. No man of sense
will believe that such prohibition would be scrupulously regarded,
without some effectual power in the government to restrain or correct
infractions of them. This power must be either a direct negative on the
State laws, or an authority in the Federal courts to annul such as might