(Reuters) – A court order demanding that Apple Inc help the U.S. government unlock the encrypted iPhone of one of the San Bernardino shooters opens a new chapter in the legal, political and technological fight pitting law enforcement against civil liberties advocates and major tech companies.

The government argues that the phone is a crucial piece of evidence in investigating one of the worst attacks in the United States by people who sympathized with Islamist militants. But privacy groups warn that forcing companies to crack their own encryption endangers the technical integrity of the Internet and threatens not just the privacy of customers but potentially citizens of any country.

A federal judge in Los Angeles on Tuesday ordered Apple to provide “reasonable technical assistance” to investigators seeking to read the data on an iPhone 5C that had been used by Rizwan Farook, who along with his wife, Tashfeen Malik, killed 14 people and wounded 22 others on Dec. 2 in San Bernardino, California.

Both were killed in a shootout with police. The Federal Bureau of Investigation has been investigating the couple’s potential communications with Islamic State and other militant groups, and argued that it needs access to the iPhone to find out more.

White House spokesman Josh Earnest said the Department of Justice was asking Apple for access to just one device, a central part of the government’s argument, which Apple Chief Executive Officer Tim Cook has said was “simply not true.”

“They are not asking Apple to redesign its product or to create a new backdoor to one of their products,” Earnest told reporters at a daily briefing.

Most technology security experts, including many who have served in government, say technical efforts to provide government access to encrypted devices inevitably brings in law enforcement. The argument has been made on and off since the 1990s, when the government tried and failed to force tech companies to incorporate a special chip into their products for surveillance purposes.

“The government suggests this tool could only be used once, on one phone,” Cook said in a statement on Tuesday. “But that’s simply not true. Once created, the technique could be used over and over again, on any number of devices.”

Representatives of several other tech companies did not respond to requests for comment on the ruling. Not surprisingly, however, trade groups that count thousands of software companies, smartphone makers and network security firms as members decried the government position, while law enforcement groups backed the Justice Department.

The industry was “committed to working with law enforcement to keep Americans safe” the Software & Information Industry Association said, but in the Apple case, “the government’s position is overbroad and unwise.”

The Computing Technology Industry Association said that if the order was carried out, “it could give the FBI the power to call for some sort of back end to encryption whenever they see fit.”

If the federal judge, Magistrate Sheri Pym, rejects Apple’s arguments, the Cupertino, California-based company can appeal her order to the district court, and then up the chain to the 9th U.S. Circuit Court of Appeals in San Francisco and ultimately the U.S. Supreme Court.

The 9th Circuit is known to be pro-privacy. “The government ultimately will have an uphill fight,” said Robert Cattanach, a former Justice Department lawyer who advises companies on cyber security issues.

Farook was assigned the phone by the county health department he worked for, prosecutors said in a court filing on Tuesday. The health department had “given its consent” to authorities to search the device and to Apple to assist investigators in that search, the document said.

San Bernardino County’s top prosecutor, District Attorney Mike Ramos, said Apple’s refusal to unlock the phone was a slap in the face to the victims of the shooting and their families.

“They’d like to know details like any of us in America would like to know. Were there other threats? Were there other individuals involved?” Ramos said in a phone interview.

‘MASTER KEY’

Dan Guido, an expert in hacking operating systems, said that to unlock the phone, the FBI would need to install an update to Apple’s iOS operating system so that investigators could circumvent the security protections, including one that wipes data if an incorrect password is entered too many times.

He said that only Apple can provide that software because the phones will only install updates that are digitally signed with a secret cryptographic key.

“That key is one of the most valuable pieces of data the entire company owns,” he said. “Someone with that key can change all the data on all the iPhones.”

The notion of opening that key is anathema to the Electronic Frontier Foundation, an online rights group. “Once this master key is created, governments around the world will surely demand that Apple undermine the security of their citizens as well,” the foundation said in a statement.

Lance James, an expert in forensics who is chief scientist with cyber intelligence firm Flashpoint, said Apple could respond to the order without providing crypto keys or specialized tools that could be used to unlock other phones.

Apple technicians could create software that would unlock the phone, allowing the company to create a backup file with all of its contents that they could provide to law enforcement, James said.

American Civil Liberties Union staff attorney Alex Abdo said the government’s request risked a “dangerous” precedent. “The Constitution does not permit the government to force companies to hack into their customers’ devices,” he said.

Apple was a topic of discussion on the presidential campaign trail on Wednesday.

Donald Trump, the front-runner for the Republican Party’s nomination to run in the Nov. 8 election, appearing on Fox News Channel’s “Fox & Friends,” said, “I agree 100 percent with the courts – in that case, we should open it (the iPhone) up. … We have to use common sense.”

Another Republican candidate, U.S. Senator Marco Rubio of Florida, called it a “tough issue” that would require government to work closely with the tech industry to find a solution. Rubio said he hoped Apple would voluntarily comply with the court order.

(Additional reporting by Megan Cassella, Doina Chiacu and Susan Heavey in Washington, Steve Holland and Joseph Menn in San Francisco, Sharon Bernstein in Los Angeles; Writing by Grant McCool; Editing by Jonathan Oatis)