His parents were both Jewish German immigrants, and his father and maternal grandfather David Einhorn were both prominent rabbis in the American Reform Judaism.
[2] Kohler was involved in a number of notable cases, including U.S. v. Bernard (the first case where postal laws were used to cover the crime of using mail for schemes to defraud), U.S. v. North American Commercial Co. (which involved the alleged liability of government for reducing the taking of seals in the Alaska seal islands under the international fur seal arbitration), three leading cases on immigration laws that reached the United States Supreme Court (Tom Hong v. U.S., Geigow v. Uhl, and Todd v. Waldman), two leading cases on bankruptcy law (re Wilcox and re Lewensohn), and U.S. v. Joint Traffic Assoc.
(in which he served as counsel for the federal government and the U.S. Supreme Court construed the anti-trust act as to railroads to embrace restraint that might be deemed reasonable).
[3] While working for the District Attorney, Kohler came into contact with another of immigration cases, first related to the Chinese Exclusion Act and later other nationalities.
He believed the Founding Fathers intended America to be a haven for refugees from all countries, and for most of his career refused to accept remuneration in immigration cases.
In his advocacy for immigrants he worked with Oscar S. Straus, Louis Marshall, Simon Wolf,[5] Abram I. Elkus, and other leaders of the Jewish community.
He managed to secure rulings which put an end to hardships immigrants suffered from due to arbitrary regulations imposed by administration officials.
In 1910, he became a member of the Board of Delegates on Civil Rights of the Union of American Hebrew Congregations and collaborated with its chairman Simon Wolf.
In 1931, he prepared two extensive briefs to attack an alien registration law passed by the Michigan state legislature and Rutgers University's intention to limit Jewish enrollment.
[8] He was a founder of the Society, was active in its council meetings, regularly wrote articles for its Publications, and served as one of its vice-president by the time he died.
[12] Several hundred people attended his funeral service in Temple Emanu-El, including United Jewish Appeal chairman Felix M. Warburg, Dr. George Alexander Kohut's widow Rebekah Kohut, Zionist Organization of America president Morris Rothenberg, Jewish Academy of Arts and Science president Dr. Henry Keller, Sarah Schottenfeld of the National Council of Jewish Women, Philip Cowen of B'nai B'rith, Oscar Leonard of the American Jewish Congress,[13] United States Circuit Court Judge Julian W. Mack, and Alfred A. Cook.