City of Solitude is (I think) the only implemented cards-can't-activate or cards-lose-all-abilities card that affects cards not in play - all the others refer to either permanents or permanent types. It works correctly for cards activated from hands, but not cards activated from graveyards or exile.

Abeyance, Hand to Hand, Pithing Needle, Voidstone Gargoyle, Sen Triplets, Suppression Field, the Split Second mechanic, and I think Brutal Suppression will have the same problem when I get around to them.