The artcle is written by an FBI agent, not a judge and is advancing legal theory that's not likely to hold up. Obama pardoned dozens of drug offenders, guilty of literally hundreds of state felonies. Presidents can and have pardoned state felons thoroughout history. They can try to push states rights as a mechanism to overcome a presidential pardon, but that's treading into theory and the courts will weigh in. And let's ne honest, State's Rights doesn't tend to do well in court. You'll note that the artcle doesn't give one single example of an actual case where a presidential pardon was granted but then overturned on State's Rights. Not in over 200+ years of presidents pardoning criminals. Let's also not forget that prior to the formation of the FBI, very very few crimes were actually federal. Limited to counterfeiting and crimes against federal politicians. Meaning that virtually all pardons issued prior were for state felony violations.