An international treaty will usually override local law, if the country is a signatory to the international law. Or sometimes the treaty is incorporated into local laws, and will therefore apply and override other laws.
But Montreal doesn’t cover advertising! So no apparent conflicts there!
While we also have the ‘*’we may substitue aircraft exceptions in Australia, I think the distinction in the NZ case was that the plane with the new seats never flew there… so it wasn’t a case of substitution. It was a case of never being offered at all.
