You can't sue ESPN for reporting the truth. They reported he tested positive, he did test positive.
The Office of the Commissioner, the a.ssociation, HPAC, Club personnel, and all of their members, affiliates, agents, consultants and employees, are prohibited from publicly disclosing information about the Player’s test results, Initial Evaluation, diagnosis, Treatment Program (including whether a Player is on either the Clinical or Administrative Track), prognosis or compliance with the Program.
They reported leaked results and in my opinion violated the confidentiality of the proceedings. They've drug his name through the mud definitively and made matters much worse than they had to be.
MLB Network is hilariously burying ESPN without mentioning them.