Section 38303xx is the section dealing with procedures for letters of resignation. Don't bother getting to excited over the U.S. codes and BUPERSMAN. Every action that the Navy takes (i.e. every document) will cite an authority, and these will generally be pretty .."general".
More "interesting" history. BUPERS used to be "The Bureau of Personnel, or maybe B. of Naval P., can't recall. So "BUPERS" regs were simply directives from the DoN Personnel department. Then they changed it to NMPC (Naval Manpower & Personnel Command) and kept the BUPERS instructions as BUPERSMAN (because the old salts hated NMPC so much they declined to change the title of the documents).
SFS
so if he resigned...he might have avoided a court martial?