I have experience working with unions in a different sector. Generally speaking without knowing the specifics of this particular agreement apart from what's been reported about it, since the mask requirement was part of the union agreement, usually the union and Disney would have to agree to drop the requirement. In my experience, Disney wouldn't be able to just drop the requirement if guests hate it, unless there's some language in the agreement giving them an out. I've never seen such a thing, but my union negotiating experience is in a different area, so maybe there is in this agreement!