He was renowned, not only thanks to his practical skill for international mediation in disputes and agreement formation skills, but also as a professor of international and labour law. He continued his academic career for more than 40 years and, among others, read political economics and constitutional law in Buenos Aires. He was president of Buenos Aires University in the years 1941-43. He published pioneering work on labour law and supported the creation of the International Labour Organisation, as well as chaired ILO’s 1928 Geneva conference. As a lawyer he was also interested in asylum, colonisation, immigration, arbitration and international peace.

In 1915 he was appointed minister of justice and education and initiated significant reforms, particularly in secondary and vocational schools, reflecting the demands of the growing industry at the time.

As the head of diplomacy, starting in 1932 he played a key role in all diplomatic issues linked with South America. He contributed to ending the war between Paraguay and Bolivia (1932-1935) by making a series of efforts which laid the foundation for the diplomatic resolution of the dispute between the two countries. In 1934 he presented the South-American Pact against War to the League of Nations. The document was signed by 11 countries. In recognition of his achievements he was elected president of the League in 1936.

He was famous for the office discipline he introduced and for his logical thinking at the conference table. At home, he was a charming host and owner of a private art collection. Lamas was always smartly dressed in perfectly tailored clothes with, as gossip had it, the highest collars in Buenos Aires.