Can't/couldn't very well do something - Idioms by The Free Dictionary
can't/couldn't very well do something
can't very well (do something)
Used to describe an inappropriate or unreasonable action that one cannot (or should not) do. I barely know the guy, so I can't very well ask him to do me this massive favor!
can’t/couldn’t very well do something (informal) used to say that something is not the right thing to do: You can’t very well change the arrangements now. It’s too late to inform people.