The Hague Convention on the Service Abroad of Judicial and Extrajudicial Documents in Civil or Commercial Matters, 20 UST361. This is the most well known service of process treaty, and includes most of the world’s industrialized countries.
Most Courts have determined that service outside the treaty procedures constitute invalid service. They have said “failure to use the treaty will have consequences.” Every treaty country can have different procedures. Each foreign country is allowed to make changes to the treaty that affects its sovereignty, such as which treaty provisions will be enforced and which will be prohibited, and whether translations will be required, and if so, into which languages. These reservations, declarations and notifications have the practical effect of allowing each foreign country to write its own treaty.