The DMCA is controversial mostly due to the changes made to title 17 section 1201. In paragraph (a) of that section is the declaration that "[n]o person shall circumvent a technological measure that effectively controls access to a work protected under this title." (See software cracking.)
Components of the DMCA may violate the First Amendment of the United States Constitution. Cases involving the DMCA have not yet reached the Supreme Court. There are efforts in Congress to modify the Act.
The DMCA implements the WIPO Copyright Treaty into US Law.