Teammates of mine have very occasionally been able to fend off a stupid edict by a mid-level manager with a simple (and literal) "Fuck off, we're busy" and/or "we have real work to do". They're usually to embarrassed to respond or escalate. It's hardly a recommended procedure, or appropriate for every situation or combination of people.

The more polite - "We're 100% contracted out right now" is somewhat less effective - they come back a month or so later.