According to the FAA, "The Pilot Records Improvement Act of 1996 (PRIA) requires that a hiring air carrier under 14 CFR part 121 and 135, or a hiring air operator under 14 CFR part 125, request, receive, and evaluate certain information concerning a pilot/applicant's training, experience, qualifications, and safety background, before allowing that individual to begin service with their company as a pilot. This process allows the entity to make a more informed hiring decision."
In its plain language, it does not list disciplinary actions, whether overturned or not. However, the court interpreted the statute to mean that "The act contains no similar prohibition regarding disclosure of records of disciplinary action taken against the individual that has been overturned. Thus, an air carrier is not required to provide records regarding disciplinary action that has been overturned, but is not expressly prohibited from doing so."
Moral of the story: be honest. Boring was being less than forthcoming and wanted to interpret the act in a way that would suit him. This is almost always a losing strategy. Alaska Airlines was simply doing what any good airline would do in finding and hiring the best pilots out there. There is no indication that Mesa went out of its way to inform Alaska of Boring's past.