I think it is a typo and should read ‘Les liens avec la France ne se démontrent plus’, which means ‘bonds with France don’t need to be demonstrated anymore’ (as in: they are now obvious or have already been demonstrated).

This is a typo, but the full context is this:

Les liens avec la France ne se démontrent plus :

«sur nos passeports libanais, c’est écrit en arabe et en français, ça veut dire ce que ça veut dire», souligne l’économiste.

Our ties to France no longer need to be shown:

"Our Lebanese passports bear writing in Arabic and French, and that means what it means", the economist underscored.

liens is better translated as ties here. Countries have ties to one another.

Also, démontrer is to prove, not to demonstrate.