Great question. A federal judge actually did rule in Harris's (and fellow former NFL player Dae'Quan Wright's) favor, clearing them to play for LSU in 2026. But LSU chose to leave both players off the Week 1 roster against Clemson anyway.
According to the wiki (from the Zxavian Harris page), LSU made this cautious call to avoid risking SEC retaliation or further legal battles — even though the court sided with them. Both players remain enrolled at LSU and can be added at any point during the season, so the door isn't closed. It's essentially LSU playing the long game and trying not to escalate tensions with the conference despite having a legal green light.