now i understand.
so, what is probably on there is just a check valve. gas can only flow one way, but you can't manually shut that line off.
up to you if you want a manual. I personally like having a manual everywhere. and they're not very expensive.
this is all assuming it is a check valve. if it's just a 1/4" MPT to 1/4" flare converter piece, then yes, at least get a check valve