Use of performance enhancing drugs should be regulated solely by the CBA's PED policy though.
You may think it should, but it doesn't. In considering the following provisions of the "Personal Conduct Policy" agreed to by the NFLPA which contains the "conduct detrimental" provisions, the league's authority to act as they have in this case is spelled out in black and white :
https://nflpaweb.blob.core.windows.net/media/Default/PDFs/Active Players/PersonalConductPolicy2015.pdf
Prohibited conduct includes, "
possession, use, or distribution of steroids or other performance enhancing substances".
Further
, "Whenever the league office becomes aware of a possible violation of the Personal Conduct Policy, it will
undertake an investigation...."
Further yet, and this is the kicker, "
League and team employees are required to cooperate in any such investigation and are obligated to be fully responsive and truthful in responding to requests from investigators for information (testimony, documents, physical evidence, or other information) that may bear on whether the Policy has been violated.
A failure to cooperate with an investigation or to be truthful in responding to inquiries will be separate grounds for disciplinary action."
Regardless of the cases at hand, there does need to be an investigative and disciplinary mechanism to address suspicions of performance enhancing drug use, even if they are legally acquired and are not detected in any test under the regime. Whether the NFLPA should have agreed to allow those powers to reside in the NFL office can be debated, but that PED discipline should be limited exclusively to positive drug tests would be a weak PED program.