During the Porfiriato, he was a prominent member of the Cíentificos, a group of technocrat advisors to President Porfirio Díaz. A noted jurist, he participated in the commissions to draft the Commercial Code (1889), the Banking Law (1897) and the Monetary Law (1905); however, his most notable work as a lawyer was obtaining the ruling favorable to Mexico in the arbitration with the United States in the Chamizal dispute. During his career, he represented Mexico in several international banking congresses. He was also a member of the Academia Mexicana de la Lengua, joining in 1904, and serving president from 1912 until his death. In 1914, during the Mexican Revolution, his mansion in Paseo de la Reforma was occupied by the troops of General Lucio Blanco; Casasús died in exile in New York in 1916.
