Board Thread:Character Discussion/@comment-5118208-20141108143108/@comment-1894786-20180304021307

True. While it's not the ideal set of powers due to the intense restrictions, being the Author does give him magic on a reality-warping level.

And he likely has a natural inclination towards magic, since Regina told him in Season 2 she could teach him magic (and as his mother, she'd definitely know whether or not he had magic/could learn magic). If Belle and the Mills family are any indication, through study or genetics, or any combination of the two, anyone can develop magical powers (or in Belle's case, the ability to cast spells).

In fact, I think Zelena, Robin Jr., Anastasia and Drizella are the only ones we've seen be born with their non-Savior magic as opposed to it being taught (Regina, Cora) or stolen (Rumple, Fiona).