CHIEF Justice John Roberts covered the breadth of American history in a U.S. Supreme Court ruling on modern technology that had unanimous support.

Law-enforcement officers will need search warrants to examine the cellphones of those placed under arrest. Exceptions exist for emergency circumstances, but otherwise the device must be secured until a judge says it is OK to look.

For generations, the nation’s highest court has wrestled with the prerogatives of law enforcement to make searches — ones to ensure their immediate safety, and gather evidence of criminal activity.

The court has tightened how far police can go in searching a car before it must be sealed up and towed away until a judge is convinced to issue a warrant.

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Roberts explained in the Wednesday ruling this all goes back to the earliest resentments of British intrusions into American homes to search as they pleased.

The twist for Roberts on cellphones is their ubiquitous nature, and their capacity beyond communications.

He even quipped that cellphones “ … are such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy.”

Cellphones contain so much private information, Roberts argued, they cannot be considered part of the personal gear that police routinely rummage through after an arrest.

Searching a phone constitutes an intrusion of privacy. Once an officer makes sure the cellphone does not a conceal a razor or similar immediate threat, the data on the phone are not a danger.

Cellphones can be secured in bags that shield them from electronic signals to prevent remote wiping of the data and the destruction of evidence.

Justice Roberts recognizes circumstances where emergency access might be necessary, and he notes that the police also have the communication tools for a fast response as well.

He also acknowledges the trade-offs inherent in the privacy protections in the U.S. Constitution:

“We cannot deny that our decision today will have an impact on the ability of law enforcement to combat crime. Cellphones have become important tools in facilitating coordination and communication among members of criminal enterprises, and can provide valuable incriminating information about dangerous criminals. Privacy comes at a cost.”

Roberts and his colleagues deftly applied an 18th-century document to 21st-century technology. This decision looks ahead.

Editorial board members are editorial page editor Kate Riley, Frank A. Blethen, Ryan Blethen, Sharon Pian Chan, Lance Dickie, Jonathan Martin, Erik Smith, Thanh Tan, William K. Blethen (emeritus) and Robert C. Blethen (emeritus).