From the 5th Circuit ruling (as quoted in the article):
DHS’s proposed approach is as unlawful as it is illogical. Under Supreme Court and Fifth Circuit precedent, this case is nowhere near moot. And in any event, the vacatur DHS requests is an equitable remedy, which is unavabile [sic] to parties with unclean hands. The Government’s litigation tactics disqualify it from such equitable relief.
Translating the legalese into plain English, the court told
LIEden's DHS that their actions and tactics have been so unlawful and dishonest that they are the basis for denying their motion.