I did [first year Law]. I also read the Constitution. The Founders made no provision for the powers Marshall gave himself. And since the Court is appointed for life, and there are NO checks and balances on what they do [aside from re-drafting laws, or amending the constitution, which is neither] the Court is, in fact, not co-equal, but superior to the other branches. And that is NOT what they intended. Something to consider before you spout off like that.
Then you didn't read it very well. What is the function of a court? It's to apply the law to a given set of facts, correct? That begs two questions: (1) how does one determine what the law is? (2) how is a particular law, once the meaning has been ascertained, to be applied to a given set of facts?
Neither of these is an easy question to answer except in the simplest of cases. They certainly aren't easy when it comes to the Constitution.
What Marshall did was to conclude, very sensibly, that since the Supreme Court was the highest court in the land, it had the final word on the precise meaning of any particular law and the final word on how that law, once the meaning was determined, applied to a given set of facts.
And the question of determining what the law is has further wrinkles. In particular, where the Constitution and federal statutory law is concerned, if there is a conflict between the two that conflict
must be navigated by a court that is trying to determine what the law is. Specifically, the court must determine whether there is a conflict, and if so which law prevails over the other as a result of that conflict. This is part of the core, fundamental meaning of what a court is; if a court cannot determine which law prevails in the case of a conflict, then it cannot apply the law to the facts, and it cannot reach a decision, meaning that there is an injury, a wrong, for which the courts are intended, which cannot be addressed by a court.
Therefore, when it comes to the Constitution, it is the courts, and ultimately the Supreme Court, that gets the final say on whether a particular statute conflicts with the Constitution, and if it does, then the Court must apply the Constitution and hold the statute unconstitutional.
But there again we revert back to the original issue: what does the Constitution mean? Again, only a court can determine that matter because it is the special province of the court to determine the law and then apply it to the facts. That means that when it comes to applying the Constitution to a given set of facts it is the Supreme Court, and only the Supreme Court, that has, or can have, the final word on the matter.
And that is
exactly what the Founders gave the Supreme Court. They made it the highest court in the land, and put it on an equal footing with the other two branches of the federal government.
The only way the Supreme Court can be trumped when it comes to the Constitution is the only way the Founders intended: amendment of the Constitution itself. The Founders expressly provided for an amendment process and therefore they clearly understood that there would be situations in which the Constitution - as applied by the Supreme Court - was found wanting, and they provided the sole way to override the Supreme Court's decisions.
They intended - or, since we can no longer cross-examine any of them in person, they must have intended (Brian Dailey Intent) - for the Supreme Court to have the final say on exactly what the Constitution meant as it was applied to a particular set of facts. If they had not, then why have a separate and co-equal court at all? If that was not to be part of the Supreme Court's purpose, then administrative courts (what are also known as non-Article III courts) would be sufficient.