At Berkeley Aschenbrenner published "State Power and the Indian Treaty Right to Fish" in the California Law Review, of which he was an editor.

[4] Later, Anthony Kennedy, who was at the time serving on the Ninth Circuit Court of Appeals, cited Aschenbrenner's essay in two appellate decisions.

[5][6] As an attorney at the Native American Rights Fund in Boulder, Colorado from 1971 to 1972, Aschenbrenner was responsible for compiling a registry of Indian law.

Aschenbrenner lectured on the subject "British and American Foundings of Parliamentary Science" at the invitation of the curators of the Rare Book Room, Library of Congress in Washington, D.C.[14][15] Aschenbrenner's second monograph "James Monroe, John Marshall and ‘The Excellence of Our Institutions'" explores the contributions of James Monroe and John Marshall to the method of Congressional precedents.

[16] In 2018, the Direction of the International Commission of the History of Representative and Parliamentary Institutions[2] elected Aschenbrenner the National Convenor for the United States.