In McCulloch v. Maryland, the Supreme Court ruled unanimously that the Constitution impliedly authorized Congress to create a national bank. Further, the Court found that the state of Maryland lacked the authority to tax the bank under the Supremacy Clause.
The Supreme Court found that under the Necessary and Proper Clause of the Constitution, Congress could create a national bank, as its creation would further Congress's ability to tax, borrow and regulate interstate commerce, all enumerated powers explicitly granted to Congress in the Constitution. This ruling in McCulloch v. Maryland established that in addition to the enumerated powers it grants, the Constitution impliedly grants Congress powers that are necessary to create a functioning government. Thus, so long as an act of Congress sufficiently relates to the orderly implementation of an enumerated power, it is constitutional.
The Supreme Court also found that under the Supremacy Clause of the Constitution, where state and federal laws conflict, federal law must triumph. As the author of the Court's opinion stated, "the power to tax is the power to destroy," and therefore the state of Maryland could not force the federal government or its created entities to pay a tax. With this ruling, the Supreme Court rejected the states' rights argument that the state of Maryland put forth.