DOJ determines what interpretation of a decision is? SCOTUS does that. Slap DOJ with an injunction.
No, the article is misleading. There are two relevant sections of the Voting Rights Act: one permits the DOJ to sue any state if its voting laws are discriminatory; the other required certain states to get DOJ approval before changing voting laws. SCOTUS struck down the second but explicitly upheld the first (indeed, it said the second section wasn't needed because of the existence of the first).