The rules to wild arcana say:
The spell must be on one of your arcane class spell lists and must be of a level that you can cast with that arcane spellcasting class.
You don't need to have the spell prepared, nor does it need to be on your list of spells known.
My opposed school is necromancy. Is it possible to use Wild Arcana to cast Enervation? The spell is of a Level I can cast (My wizard is CL 7) but I am not sure whether opposed spells are on my arcane class spell lists.