A leading US civil liberties group has said that the government should not "commandeer" tech companies to work at the behest of law enforcement.
The American Civil Liberties Union (ACLU) filed a "friend of the court" brief on Wednesday in support of Apple, which is currently fighting a court case against the FBI.
In February, a California court said the iPhone maker should help federal agents break into the iPhone of one of the San Bernardino shooters.
Apple refused to comply with the order, arguing that the order compelling it to rewrite software that would help the FBI bypass the phone's passcode would violate the company's First Amendment rights.
The civil liberties group's lawyers agreed, arguing that the court order would practically make the company a de facto arm of the FBI.
"Law enforcement may not commandeer innocent third parties into becoming its undercover agents, its spies, or its hackers," the group's lawyers said in the brief.
The ACLU said that the government's interpretation of the ruling could be wide-ranging if it wins the case. The brief said the government could go on to undermine potentially millions of its own products by forcing Apple to "deliver similar signed software using Apple's automatic-update infrastructure."
"Simply put, what the government seeks here is an authority that would undermine American and global trust in software security updates, with catastrophic consequences for digital security and privacy," the brief added.
Amazon, Google, Facebook, Microsoft, and Yahoo have all said they would file similar briefs supporting Apple.
Apple on Tuesday filed an appeal in the case on Tuesday, hours before its two-week deadline expired.
A spokesperson for Apple did not immediately respond to a request for comment.