[@Archmage MC]
For regeneration fruit, there was marco's technically, and it was nullfied temporarily by seastone, but that's not quite the same as haki.f

For Haki? Well, we've confirmation that it ignore's luffy's rubberyness (which isn't armor, or a shield of any kind, mind you) and harms him regardless, while not even stretching him iirc. I guess it could be argued that haki directly harms the soul, or spirit, which makes a lot of sense, but even in this case, I doubt having your spirit [i]cut in half[/i] would be uh... Lethal.

I'll let [@Jensoman] say his part. Seeing how toonforce doesn't have that many real offensive options, I don't think it'd be too much of an issue for of its abilities to be allowed.