An article from the The Times Picayune on the matter, and a quote:
The U.S. Justice Department is suing Louisiana in New Orleans federal court to block 2014-15 vouchers for students in public school systems that are under federal desegregation orders. The first year of private school vouchers “impeded the desegregation process,” the federal government says.
The Justice Department’s Memorandum in Support can be seen here.
Another article here.