I think I would have said no too.
But the other mother was probably in desperate need and didnt know what you were going to say so probably thought she'd have a try.
If she 'demanded' it, then that would have been totally unacceptable.
I agree with this. And saying no was probably the right thing to do anyway, because if he was already running amok, then he'd really crack the sads if he was restrained in a highchair after having the freedom!

Unhappy child in a highchair in a busy restaurant = unpleasant dining experience

Corelly x