WASHINGTON – When Apple said no to the FBI order to unlock an iPhone used by one of the San Bernardino terrorists, a debate between privacy advocates and national security officials erupted. But the tension between those two interests is as old as the Bill of Rights.

Robert Litt, who is general counsel to the Office of the Director of National Intelligence, argued last month that Fourth Amendment protections should be reconsidered to keep up with modern technological changes.

“It’s time that we stop trying to hammer 20th century pegs into 21st century holes,” Litt said.

The Fourth Amendment is often used as the basis for protecting the privacy of Americans from government intrusion.

It holds, in part: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause…”

But Litt said the reasonableness of searches must be balanced against government interests.

“The ‘reasonableness’ of a warrantless search depends on balancing the ‘intrusion on the individual’s Fourth Amendment interests against’ the search’s ‘promotion of legitimate governmental interests.’”

Litt proposed that privacy law should focus on attributing what is “unreasonable” government behavior rather than on determining what constitutes a government “search.” In cases that require determining whether government activity is reasonable in the digital age, Litt said, the Fourth Amendment does not apply.

Courts ruling on government searches should consider “factors such as whether the information is content or noncontent, whether it’s publicly exposed through social media or stored in the equivalent of cloud,” he said. “Or whether the exposure is voluntary over the most technical set of criteria in modern day.”

The question then becomes what constitutes probable cause and reasonable expectation of privacy in the digital age, when 68 percent of U.S. adults own a smartphone and almost all of the digital data on those devices is exposed to third parties.

But Jim Harper, a senior fellow at the libertarian Cato Institute, technology has nothing to do with whether the Fourth Amendment always applies in privacy disputes.

Smartphones, he argued, are indisputably protected by the Fourth Amendment.

“They have all of the qualities the framers of the Constitution wanted to protect when they wrote the Fourth Amendment,” said Harper. “They didn’t know what the future would be like or that we’d have these but it’s a thing much like the things—a case or a valise or whatever else– people carried at the time.”

The laws do not allow the government to make Apple rewrite its operating system, according to Harper.

“What the government is asking Apple is to do labor for the government,” Harper said. “[The government order] goes another step beyond that, I think, to require Apple to break one of its products.”

Some experts like Paul Rosenzweig, former assistant secretary for policy to the Department of Homeland Security, argue that decryption, much like technology itself, is neutral and only violates the law when it is used to do so.

“Technology, decryption and surveillance can be put to good or bad uses,” he said. “If we could build a decryption system that would only be used under a rule of law, with the judge’s approval, probable clause and a warrant, then I’d probably be for it.”

But Rosenzweig believes the “reasonable expectation of privacy” precedent from Katz v. United States in 1967 should be revisited. Reasonable expectation of privacy then referred to what society “objectively deemed reasonable.”

“It was criticized even back when it was written for being horribly circular and changing,” Rosenzweig said. “In 2000 my reasonable expectation was that nobody would make me take my shoes off at the airport. Today I have the opposite expectation because somebody changed the rules. We should change it to ‘reasonable expectation of when not to be interfered with by the government.’”

However, Rosenzweig warned that the digital data smartphone users share, through downloaded apps or on the cloud, is not protected by the Fourth Amendment.

“The Constitution by and large is mostly not relevant because of a longstanding rule that the data you give to a third party … is not yours to control,” he said.

Harper said digital privacy shouldn’t just rely on legal protections. The architecture of the Internet also needs to be revamped to protect the privacy and safety of smartphone users from hackers, attackers and even the government,” he said.

“Laws are pretty darn fallible,” Harper said. “The Internet should naturally be better at protecting and be more secure, more concealed so that as there are more changes to technology, you don’t actually have to rely on laws for the protection of privacy.”