Apple has said modifying the iPhone operating system could crash a mobile phone network's masts or allow people to avoid paying for phone calls.
The claims are Apple's contribution to the US Copyright Office's regular review of the Digital Millennium Copyright Act (DMCA), a law that forbids the circumvention of copy control mechanisms.
Apple says that modification of the phone's software, a process known as jailbreaking, could lead to major network disruptions. Jailbreaking gets around the copyright control features that prohibit, for example, the installation of applications unapproved by Apple.
Apple's arguments, filed June 23, seek to rebut a request to the agency by the digital rights group Electronic Frontier Foundation (EFF) that modifications to the iPhone's software do not violate the DMCA and should be allowed.
The U.S. Copyright Office holds hearings every three years to consider requests to make exceptions to the nation's copyright law.
Jailbreaking continues to be popular with iPhone users, who can also then use their devices on the networks of operators who have not signed distribution deals with Apple.
Apple argues that the practice constitutes copyright infringement. No one has been prosecuted for jailbreaking, although Apple discourages it.
Apple's latest filing describes potentially severe technical problems operators could face with jailbroken phones.
Since the OS code is accessible on a jailbroken phone, Apple said it would be possible to reprogram one to gain access to the phone's BBP (baseband processor), which controls the connection to the operator's network.