Article 25 Montreal Convention
Article 25 of the Montreal Convention (Convention For the Unification of Certain Rules for International Carriage by Air) is titled Stipulation on Limits. It is under Chapter III (Liability of the Carrier and Extent of Compensation for Damage).
A carrier may stipulate that the contract of carriage shall be subject to higher limits of liability than those provided for in this Convention or to no limits of liability whatsoever.
See also: Article 24 Montreal Convention