...can’t be obeyed.” That was theadvice of General Douglas MacArthur. It makes perfect sense: Those who receive such an order will find you foolish, perhaps even incompetent. Career suicide.
But never forget this variant either:
...won’t be obeyed.” Issue a command that people disregard because you’ve allowed them too much power to write their own rules and your demise as a leader will be slower and more painful as you lose authority and respect incrementally.