Ignore it. You might have a modest case for copyright violation for duplication of pages. However, prosecuting it would waste money and man-hours that are best

Ignore it. You might have a modest case for copyright violation for duplication of pages. However, prosecuting it would waste money and man-hours that are best spent elsewhere, and also possibly frighten them into aggressive improvement. "Winning" would likely be a net loss. Your best strategy is to let them coast and hope they are gradually left behind. If they developed a habit of laziness, don't help them break it!