[spoiler discussion] Could Regulus be sealed

Could regular sealing magic work on Regulus? or would he just be unaffected.

Furthermore would Ol Shamak work on Regulus? It WAS basically meant to seal witches. I assume regulus could get hit with it, since he constantly takes on attacks as he knows he's invincible.

If he was serious about attacking i dont think it'd be possible to get close to use Ol Shamak, but assume it is arc 5 regulus and the battle goes the way it went but instead Al shows up and uses Ol Shamak could that defeat regulus?

Or does his authority's invincibility also extend to seals and stuff