[3][4] From 1923 to 1925 on behalf of the ACLU, Nelles and a young Walter Pollak argued Gitlow v. New York before the United States Supreme Court against a conviction for "advocacy of criminal anarchy.
"[5] The court upheld Gitlow's conviction but recognized that the due process clause of the 14th Amendment incorporated, which protected fundamental provisions of the Bill of Rights, including the freedom of speech.
)[6] Throughout the 1920s, Nelles participated in a loose partnership of left-wing attorneys, including Joseph R. Brodsky, Swinburne Hale, Carol Weiss King, and Isaac Shorr.
[2] The liberal Nelles also sought to mediate sectarian fighting among American radicals, sitting with Roger Baldwin and others on a special committee established in August 1922 to investigate charges levied by Abraham Cahan and The Jewish Daily Forward that the Friends of Soviet Russia (FSR) organization (for which he served as attorney[9]) was engaged in the misappropriation of funds raised for the relief of famine in Soviet Russia.
[10] The committee ultimately exonerated the FSR of these charges, but Nelles declined to sign the final report because he was appointed as a law partner as counsel for that organization, a circumstance that created a potential conflict of interest.
[8] Holding pacifist beliefs himself,[13] following the entry of the United States into World War I in April 1917 Nelles was persuaded by his old college classmate Roger Baldwin to leave his practice to become house counsel for the fledgling National Civil Liberties Bureau (NCLB) of the American Union Against Militarism that Baldwin had helped launch.
The Civil Liberties Bureau in its first years dealt primarily with cases involving conscientious objectors and political opponents of the war who faced charges under the so-called Espionage Act.
[2] The offices of the National Civil Liberties Bureau were raided by the Department of Justice on August 30, 1918, by agents who seized all of Nelles' files.
Roger Baldwin later fondly recalled their partnership: We made a team which was never after equalled in the American Civil Liberties Union.