He served in that capacity until February 1, 1945, when Sam Bass Warner was appointed the fourth Register of Copyrights.

Richard Crosby De Wolf is noted for being one of the earliest teachers of copyright law as a separate subject in the United States.

[1] De Wolf is also noted as one of the earliest scholars to suggest a completely disjunctive reading of the Copyright Clause.

[1] The Clause, which gives Congress the power to grant both copyrights and patents, states The Congress shall have Power ... To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.De Wolf wrote in his book "An Outline of Copyright Law" that one could resolve this statement disjunctively, illustrating the separate grants of authority for copyrights and patents, so that it states "(1) The progress of science is to be promoted by securing to authors the right to their writings; and (2) the progress of useful arts is to be promoted by securing to inventors the right to their discoveries."

The Supreme Court endorsed this view in 1966 in Graham v. John Deere Co., citing "An Outline of Copyright Law."