> "Do not jump over or duck under this ribbon, or cut it!", that's, for the DMCA, enough - so you get into fun games where you claim that
No. There must be an effective technological measure (objectively, according to the state of the art); see https://www.law.cornell.edu/uscode/text/17/1201 (a)(1)(A): No person shall circumvent a technological measure that effectively controls access to a work protected under this title.