The Washington Convention is in the form of a text of 16 articles stating the obligations accepted by Contracting States: the most important of these is to introduce the Uniform Law annexed to the Convention into their respective national legislation. This Uniform Law provides 15 articles governing the form of the international will.
The Convention does not aim at harmonising or unifying the forms that already exist in the different systems of national law.
These are neither abolished nor modified. It simply proposes, alongside and in addition to the traditional forms, another new form which it is hoped practice will bring into use mainly but not exclusively when in the circumstances a will has some international characteristics.
The provisions of the Uniform Law deal only with form in the strict sense: all questions which may in certain respects relate to rules of substance such as the personal capacity required of the testator or of the witnesses, the joint will, have been left aside, as have questions relating to the revocation, destruction or modification of wills.
(Excerpt from the Explanatory Report published on this site)