Voter ID cases could let John Roberts destroy Voting Rights Act.

Striking down or significantly narrowing that key pillar, known as Section 2, would essentially render the most successful civil-rights law in U.S. history a dead letter. In a nutshell, Section 2 prohibits racial discrimination in voting.

Since Congress amended it in 1982, Section 2 has barred not only voting laws that are intended to discriminate against minorities, but also those that have the effect of discriminating. That’s largely because, these days, very few people in power explicitly declare an intention to racially discriminate, so a law that banned only intentional discrimination would be virtually useless.

But many conservatives, including John Roberts, think the “effects” standard is too broad. As a young lawyer in the Reagan Justice Department, Roberts wrote a memo opposing that 1982 move by Congress to broaden Section 2 to cover laws with discriminatory effects, saying it would “raise grave constitutional questions.” The 14th and 15th Amendments explicitly ban only intentional discrimination.