Actually now. The Hammonds were convicted under laws that called for a mandatory five year minimum sentence. The jury sentenced them to terms that were less than that. A court ordered them back to jail because that's what the law required. Now if your argument is against mandatory sentences then I may not disagree with you. But there isn't any double jeopardy issues here.
“A new law” is the basis for Double Jeopardy. That’s why they call it ‘time served’. And not ‘time served until they pass a new law’.