I don’t know if you’ve noticed, but “donald trump cannot [xyz] because [abc]” is not a phrase that has meaning anymore in this country, as far as I’m concerned. . . . If I’m wrong, I’d love to hear how.
He can initiate whatever he wants, in this case issue a pardon for someone whose crimes are not federal, but his power does not lie in what he can or cannot initiate or claim, and it never has.
His power -- which he is losing rapidly -- has always rested in other people, in the belief and action of everyone underneath him who carry out his dictates. Belief that if x happens, y is likely to follow, belief that if they personally do not act then someone else can and must act. Especially when it comes to the law.
But now he's done a very stupid thing and upended all that certainty upon which his power stood.
As you imply, he can initiate a pardon to anyone, anywhere, for anything. But when he does so without basis in law, and those who would carry it out see it as optional at best, ultimately it weakens him in ways he doesn't even understand.
Like this. Colorado has ignored his pardon of Tina Peters and will likely ignore any others that have no basis in law, and any other state can follow. There is no requirement that any state honor a pardon based on powers that were never granted, making the whole thing optional -- and showing others who might be inclined to honor it anyway that there's no need.
This is the nature of real power. It's not something he can change or alter.