A non–copyrighted work can still have a copy protection measure

But would the DMCA ("Copyright Act") still apply when there's no copyright?

Here, let's read together: https://www.law.cornell.edu/uscode/text/17/1201

> No person shall circumvent a technological measure that effectively controls access to a work protected under this title

> protected under this title

A work not protected under title 17, copyright, is thus not covered.