17 U.S.C. § 408(a)—Copyright registration

(a) Registration Permissive.—At any time during the subsistence of the first term of copyright in any published or unpublished work in which the copyright was secured before January 1, 1978, and during the subsistence of any copyright secured on or after that date, the owner of copyright or of any exclusive right in the work may obtain registration of the copyright claim by delivering to the Copyright Office the deposit specified by this section, together with the application and fee specified by sections 409 and 708. Such registration is not a condition of copyright protection.