The rhetoric in the D.C. battle over a major piece of online antipiracy legislation is that it would either save jobs or kill innovation, but there were moments during a Wednesday congressional hearing when such simple arguments gave way to discussion of more complex issues such as the liability of Internet service providers, search engines and other tech firms to root out copyright infringement on websites.

The House bill, called the Stop Online Piracy Act, is a companion piece to Senate legislation that passed the Judiciary Committee unanimously in May. Both bills are aimed at rooting out so-called rogue websites, overseas sites devoted to selling unauthorized content like movies, TV shows and music.

On Wednesday, timed to the House Judiciary Committee’s hearing on the proposed legislation, a number of tech firms including Google, Facebook, eBay and Twitter published a full-page ad in the New York Times claiming that the legislation “would seriously undermine the effective mechanism Congress enacted with the Digital Millennium Copyright Act,” which includes a “safe harbor” provision in which Internet firms are shielded from liability if they take steps to quickly remove infringing material from their sites. This usually happens if they get a takedown notice from a copyright owner.

Testifying before the committee, MPAA senior exec VP Michael O’Leary said that while the safe harbor provision works “with varying degrees of effectiveness,” the rogue websites and cyberlockers covered by the new legislation “are not legitimate.” “They do not act in good faith,” he said. “They do not comply with DMCA requests, because their purpose is to traffic in stolen content.”

U.S. Register of Copyrights Maria Pallante said that the legislation would “sit next to” the DMCA, not replace it, and that the “notice and takedown system will remain intact.”

The legislation would expand the attorney general’s ability to seek injunctive relief against foreign sites that traffic in infringing goods, but tech firms are concerned over efforts to choke off support of such sites by requiring owners of domain names to disable links and ISPs to block domain names. They also claim that the legislation allows a “private right of action,” in which content owners can seek their own injunctive relief against payment processors and ad firms. The House version requires that copyright holders contact payment processors and ad firms first before going to court.

Google policy counsel Katherine Oyama said that Internet startups base their business models on the safe harbor provision but worry that the language of the new legislation is so broad in scope that they fear it will open them up to liability unless they “proactively monitor user-generated content.”

Instead, she said, Google and other firms favor more narrowly tailored legislation aimed simply at choking off the money from ad firms and payment processors. Rep. Darrell Issa (D-Calif.), another critic of the bill, suggested that instead a court of continued jurisdiction should be set up — similar to the International Trade Commission — that could streamline the process to identify infringing sites.