I assumed it was a pardon since that technically is within his power. But to grant felons the right to vote without legislation?
You aren’t kidding!
You can read the full text of the Virginia Supreme Court ruling here: https://lintvwavy.files.wordpress.com/2016/07/scotus-mcauliffe-voting-rights.pdf
Bottom line, what McAuliffe tried to do with his blanket restoration of civil rights to the 206,000 felons (probable Democrat voters) was to use the proper authority granted to a Virginia Governor, yes, but in a fashion obscenely far beyond the purpose for which it was intended. It was intended to allow a Governor to grant clemency, on a case-by-case basis, for those individual former felons who turned themselves around and became productive citizens after they "paid their debt to society" via prison-time. Nothing more.
What McAuliffe brashly attempted was a brazen bastardization of gubernatorial clemency. Had he succeeded, it would have made a mockery of the clemency powers granted. Thankfully, the Virginia Supreme Court still had some Constitutionalists on it. Even so, it was still a four to three ruling: yep, three of our Virginia Supreme Court justices were perfectly fine with McAuliffe's brazen bastardization.