Simplify the following text for a Grade 12 native English-speaking person.
Original: An international conference on passports and through tickets , held by the League of Nations in 1920 , recommended that passports be issued in French , historically the language of diplomacy , and one other language .
Simplified: In 1920 , the International Conference on Passports , Customs Formalities and Through Tickets made a law that said passports must be issued in French and at least one other language .