to be not for somebody to say
01
to believe that it is not someone's place to make a decision or judgment on a particular matter and that it should be left to others who are more qualified or have more authority to do so
例
It is not for him to say whether we should go or stay.
Look, I agree with you, she should be punished for what happened. But she's not our daughter, so it's not for us to say!
