Well, the power of the Supreme Court to declare or treat an act of Congress as unconstitutional and therefore unenforceable was not deemed to be obvious to everyone when Marbury v. Madison was decided in 1803. I don't think that you will find that power to be clearly provided for in the Constitution. Moreover, I think that the lack of any clear textual support for that power is very helpful in understanding why the Court has for the most part exercised that power more sparingly than it might have exercised a power for which there existed clear constitutional authority.
A few things need to be cleared up. First of all, the supreme court has no power to determine findings of fact, but only whether or not the law was properly applied. When the Constitution gives Congress the power to enforce anything, it's not overriding Articles II and III; it's simply giving Congress the power to empower the proper executive and judicial authorities to do their job in enforcing the law - particularly by specifying what the consequences should be for violating it. It does not give Congress the power to pass new restrictions on activity, or to actually conduct investigations and proceedings themselves.
Now, although SCOTUS can't make any determinations of fact themselves, they can examine the proceedings of lower courts, to determine if the rules of presenting and examining evidence were properly observed. But there has to be a lower court ruling to begin with, which there apparently wasn't, in this case; Congress decided to become judge, jury, and executioner all on their own, which, IMHO, is flagrantly unconstitutional. The proper way of handling it would be the same way government handles any discrimination complaints in the private sector: by having the proper (Congress-appointed) authorities investigate to determine whether or not unlawful discrimination is occuring, and to take appropriate corrective action in those particular cases where it is found to be occurring.
None of our branches can perform its function without making factual determinations. How can the Congress be expected to appropriate funds for the construction of a new post office in your city without first making the factual determination that a new post office is needed? And if there already exists two post offices within one block of your home and the Congress decides to build another post office on your block, do you think that the judicial branch has the power to decide that the Congress is mistaken in its factual determination that the third post office is necessary?
And if the Congress were to make a factual determination that too many traffic accidents are caused by vehicles which are colored red, white and/or blue rather than green and based on that finding passed a law requiring that all postal trucks be painted green, do you think that a court has the power to decide that the Congress's factual determination is incorrect and that blue postal trucks would actually be safer?
This is the essence of the problem that is faced by any Supreme Court which wishes to be an "activist" court and decide that Congressional acts are in excess of the Congress's constitutional powers. If the Congress makes the factual determination that certain states are using literacy tests to deny or abridge the right of citizens to vote based on their race and that it is necessary to suspend the literacy tests in order to enforce the Fifteenth Amendment, what legitimate procedures exist for the Court to determine that the Congress's factual determinations are incorrect?
I'm not sure why there was so much controversy over it. It was explicitly anicipated in the Federalist Papers, and Article III, Section 2 states, "The judicial Power shall extend to all Cases, in Law and Equity, arising under this Constitution...." Elsewhere, it states that the Constitution itself is indeed law ("the supreme Law of the Land"), so therefore the courts clearly have the power to apply it, as they would any other federal law.
None of our branches can perform its function without making factual determinations. How can the Congress be expected to appropriate funds for the construction of a new post office in your city without first making the factual determination that a new post office is needed?
Congress can make factual determinations to do what they have the power to do. In the case of enforcing the 15th amendment, they have the power, as I said in the previous post, to appoint the officers and define the procedures for dealing with the lawbreakers. Information that they might need in order to pass such legislation would include: the number of polling places throughout the country, particularly in the areas where compliance is likely to be a problem; the success or failure which current procedures have had in ensuring compliance; the tactics that lawbreakers use in order to cover their activities - these are things that would help determine how much funding is needed to support the authorities, what agencies they should be allowed to share information with, what their command structure should be, and what the consequences should be for violating the law. They do not need to make investigations to determine what kinds of additional practices should be outlawed, because they don't have the power to outlaw them in the first place.
And if there already exists two post offices within one block of your home and the Congress decides to build another post office on your block, do you think that the judicial branch has the power to decide that the Congress is mistaken in its factual determination that the third post office is necessary?
No, of course not. If Congress is given the power to establish post offices, they can establish as many as they damn well please. In the case of outlawing literacy tests, the issue isn't whether or not Congress' facts are correct, because that's irrelevant. The only issue is whether or not they have the power to outlaw such tests to begin with, which they don't.
If the Congress makes the factual determination that certain states are using literacy tests to deny or abridge the right of citizens to vote based on their race and that it is necessary to suspend the literacy tests in order to enforce the Fifteenth Amendment, what legitimate procedures exist for the Court to determine that the Congress's factual determinations are incorrect?
It is not necessary, and certainly not proper, by any stretch, to suspend a lawful practice in order to enforce an unlawful practice. As I mentioned, the authorities go after businesses all the time for violations of anti-discrimination laws, without there being any need for suspending the use of the ordinary criteria business use to screen employees, regardless of whether or not some businesses have been dishonestly applying those criteria in a discriminatory manner. It's no different with screening of voters. States have the right, under the Constitution, to use whatever screening criteria they choose, except for race, color, previous condition of servitude, gender, payment of poll taxes, and age, for those over 18. Everything else is fair game, and indeed protected by the Constitution from congressional interference. The only thing the federal authorities have the power to do is take action against specific violators, or suspected violators, when they've determined that there have been, or are likely to have been, violations of the rules I mentioned above.