The history of international protection starts with the League of Nations.
In 1921, the first Office of the High Commissioner for Refugees was founded; later, several institutions were created to adopt some or all of the tasks of the High Commissioner: the Nansen International Office for Refugees (1931-1938), the Office of the High Commissioner for Refugees coming from Germany (1933-1938), the Office of the High Commissioner of the League of Nations for Refugees (1939-1946) and the Intergovernmental Committee on Refugees (1938-1947).
The Convention Relating to the International Status of Refugees of 1933 is a milestone in the protection of refugees and served as a model for the 1951 Convention. Its Article 3 reads:
“Each of the Contracting Parties undertakes not to remove or keep from its territory by application of police measures, such as expulsions or non-admittance at the frontier (refoulement), refugees who have been authorized to reside there regularly, unless the said measures are dictated by reasons of national security or public order.
It undertakes in any case not to refuse entry to refugees at the frontier of their countries of origin. I
t reserves the right to apply such internal measures as it may deem necessary to refugees who, having been expelled for reasons of national security or public order, are unable to leave its territory because they have not received, at their request or through the intervention of institutions dealing with them, the necessary authorizations and visas permitting them to proceed to another country.”
The Convention of 1933 was ratified by nine States, including France and the United Kingdom, the most important powers of that time.The UK did not, however, accept the second paragraph of Article 3. Nevertheless, it was by virtue of this Convention that the principle of non-refoulement acquired the status of international treaty law.
Taken from: Gilbert Jaeger: On the history of the international protection of refugees, Form IRRC September 2001 Vol. 83 No 843 727:
League of Nations, Convention Relating to the International Status of Refugees, 28 October 1933, League of Nations, Treaty Series Vol. CLIX No. 3663, available at: http://www.unhcr.org/refworld/docid/3dd8cf374.html [accessed 1 April 2011]
You can find the full text of the Convention in the pdf-document on the left side.