That would be useful. A command that bans / blocks item in your Hand.

Something like /blockitem ban GLOBAL hand

That would be very useful.

It already does and has forever?

• ban [dim list] [item[:*:meta]] - Bans the item. (Defaults to the item you are holding and the dimension you are in.)
• unban [item[:*:meta]] - Unbans the item. (Defaults to the item you are holding and the dimension you are in.)

Thus if you do /blockitem ban __GLOBAL__ whatever you are holding will be banned. Including all subsets of that item. If you want a meta specific ban you need to type it.