What is Section 4?
By striking down Section 4, the US Supreme Court just dismantled the entire framework of the Voting Rights Act of 1965. Section 4 determines how we impliment anti-discrimination voting laws. While Section 5 -- the legislation that was actually being contested -- is still intact, Section 4's unconstitutionality means that legislators have no basis to enforce Section 5.
Here is how the Department of Justice describes Section 4:
The leading opinion tried to lessen backlash to its decision by saying, "Our decision in no way affects the permanent, nationwide ban on racial discrimination in voting found in [Section] 2. We issue no holding on [Section] 5 itself, only on the coverage formula. Congress may draft another formula based on current conditions."
The vote was 5-4, with the liberals dissenting. Justice Ginsberg said, "The sad irony of today’s decision lies in its utter failure to grasp why the VRA has proven effective."