A decision by a U.S. government agency prohibiting the transmission of 3D dental records into the U.S. could open the door to further content restrictions on the Internet, digital rights groups have said.

The heart of the question is whether the U.S. International Trade Commission can block digital goods, in additional to physical ones, from being imported to the U.S. The Motion Picture Association of America has watched the agency's decision closely, with an eye on using the USITC to block websites.

The USITC's decision concerns a patent dispute between two companies that make clear dental braces, but it could have larger consequences and is the wrong way to deal with infringement complaints, the rights groups said Friday in a letter to the agency.

The order, from 2014, requires the Pakistani operations of a U.S. dental company, ClearCorrect, to stop uploading 3D maps of patients' teeth to ClearCorrect's U.S. servers. The USITC based its order on a finding of patent infringement, but the decision has "enormous ramifications, opening the door to Internet content blocking efforts rejected by Congress and the public," said the letter, from 16 digital rights groups and 12 law professors.

The USITC ruling may give the MPAA and other copyright owners a new tool to block Internet content, critics said, even though the MPAA failed in 2012 to get Congress to pass the controversial Stop Online Piracy Act [SOPA]. SOPA would have required Internet service providers to filter out the domain names of websites accused of copyright infringement, and required search engines to block those sites.

The USITC has the authority to investigate patent and copyright complaints filed by U.S. companies and block the import of infringing goods. The agency's ruling against ClearCorrect followed a complaint of patent infringement from competitor Align Technology.

The agency's past patent cases have largely focused on physical goods, not digital information, and the ClearCorrect case hinges on whether the "articles" the USITC can block from import under U.S. law includes digital goods.

Driving the concern from the digital rights groups signing onto Friday's letter -- including Public Knowledge, the American Civil Liberties Union and the Electronic Frontier Foundation -- is a push by the MPAA to use the ClearCorrect case as precedence for getting the USITC to block digital transmission of movies it believes infringe copyright.

In December, news organizations published a leaked MPAA memo suggesting the trade group could use the USITC to force ISPs to block subscriber access to movie piracy websites.

The USITC has the authority "to order network access ISPs to cease and desist from providing their subscribers with access to pirate sites" if the agency finds that the ISPs are violating copyright law by distributing infringing works, said the memo, written by MPAA lawyers last April.

The MPAA filed a brief in support of the USITC's decision, saying its authority to issue cease-and-desist orders should apply to digital, as well as physical, goods. Infringement is "shifting to downloadable formats," the USITC said, reflecting the MPAA's opinion filed in the ClearCorrect case.

Last month, Align and the USITC filed briefs to the U.S. Court of Appeals for the Federal Circuit, where the agency's ClearCorrect ruling is now under appeal. Align accused ClearCorrect of infringing seven dental imaging-related patents, and the agency found ClearCorrect infringed six of them.

While Align and the USITC argue the agency's asserted authority over digital goods would have a "minimal" impact on the Internet, they ignore the MPAA's argument that "took a precisely contradictory position," said Charles Duan, director of the Patent Reform Project at Public Knowledge.

The MPAA memo "turned what was initially a hypothetical concern into an actual threat to the Internet," he added by email.

The MPAA believes Congress has given the USITC "broad authority" to protect U.S. industries from unfair acts, including copyright infringement, the trade group said in a statement. "Undercutting the ITC's jurisdiction in this area will hurt the rapid growth of domestic and international marketplaces for distributing content digitally, and ultimately undermine the commission's mandate to protect American businesses," the MPAA added.