Yes, sir, I'm afraid that's true, sir.
In post 112, I quoted to you a paragraph from a relevant Supreme Court opinion:
"Meanwhile, beginning in 1890, the States of Alabama, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Virginia enacted tests still in use which were specifically designed to prevent Negroes from voting. Typically, they made the ability to read and write a registration qualification and also required completion of a registration form. These laws were based on the fact that as of 1890 in each of the named States, more than two-thirds fo the adult Negroes were illiterate while less than one-quarter of the adult whites were unable to read or write. At the same time, alternate tests were prescribed in all of the named States to assure that white illiterates would not be deprived of the franchise. These included grandfather clauses, property qualifications, 'good character' tests, and the requirement that registrants 'understand' or 'interpret' certain matter."
Because if the election officials were in fact using race, not literacy, as a criterion, then federal authorities would have had the power to act, even without Congress passing a new law. It's called investigating, determining probable cause, making charges, conducting judicial proceedings, etc., you know, that whole 'due process' stuff.
To begin with, the Constitution does not contain any provisions calling for criminal sanctions for its violation. The "federal authorities" (by which I assume you mean the Department of Justice/FBI) don't have the power to do anything "without Congress passing a . . . law." Aside from the President and Vice-President, the entire executive branch of the Federal Government has no right to even exist “without Congress passing a . . . law.”
In response to the Voting Rights Act, one of the arguments made by South Carolina was that Congress’s power under Section 2 should be interpreted very narrowly so that this congressional power would be limited to occasional meaningless legislation reminding states that of their obligations under the Fifteenth Amendment. This was the Court’s response to that argument:
“We therefore reject South Carolina's argument that Congress may appropriately do no more than to forbid violations of the Fifteenth Amendment in general terms - that the task of fashioning specific remedies or of applying them to particular localities must necessarily be left entirely to the courts. Congress is not circumscribed by any such artificial rules under 2 of the Fifteenth Amendment. In the oft-repeated words of Chief Justice Marshall, referring to another specific legislative authorization in the Constitution, ‘This power, like all others vested in Congress, is complete in itself, may be exercised to its utmost extent, and acknowledges no limitations, other than are prescribed in the constitution.’”
And do you notice that in that case it was the state of South Carolina that rested all of their hopes on finding some "activist" Supreme Court justices to declare a law unconstitutional?
Sorry, my bad. I missed that part. So anyway, that means that the federal government has the power to crack down on literacy tests - or any other types of tests - that are improperly administered with a racial bias, but Congress does not have the power to outlaw literacy tests that are not administered with a racial bias. Like I said, if the authorities need to take action, then they need to investigate actual cases, and take the type of action that any law-enforcement authorities would when they suspect an illegality of some sort.
And yes, the authorities do have the power to institute criminal proceedings, provided Congress vests them with such, but that doesn't mean that Congress has the power to do so with regard to actions that do not violate what the law says. In short, Section 2 in no way gives Congress the power to create new prohibitions, but merely to define the procedures and consequences that flow from violations of existing constitutional prohibitions.