The Fourth Amendment to the U.S. Constitution is unambiguous. It says, “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, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Today that right to privacy is under siege by the U.S. government. It collects vast amounts of data on the personal transactions and communications of Americans.

The unfolding story on the National Security Agency reveals that the data are being used, in the words of The New York Times, to “create sophisticated graphs of some Americans’ social connections that can identify their associates, their locations at certain times, their traveling companions and other personal information.” It has also collected data about the location of Americans’ cell phones, allowing the movements of U.S. citizens to be tracked by the government.

We are assured by President Obama and congressional leaders that this activity by the National Security Agency is all perfectly legal and an essential part of the government’s effort to prevent terrorist attacks.

How could the law have drifted so far from the clear intent of the Fourth Amendment regarding “probable cause” and narrowly defined searches necessary for public safety?

One cause is the Patriot Act, which has been broadly interpreted by the government to allow untrammeled access to American’s personal information.

That interpretation relies on a Supreme Court ruling that leans toward strengthening police powers by the notion that personal information is not protected once it passes from an individual to a third party, such as your mail carrier, your Internet provider, your telephone company or your bank.

A broader interpretation of the Fourth Amendment is essential in light of the ability of service providers using modern computers to keep voluminous records that can be easily accessed to discover extensive and intimate details of any individual’s life. The government should not be permitted to collect such information on Americans except upon “probable cause … supported by Oath or affirmation” that it is needed for a specifically targeted public purpose.

American citizens should be able entrust their security to government agents without giving up their right to privacy in the ensuing exercise of that authority.

Congress should move to restrain government agencies bent on extending their reach into individual privacy with the ever more powerful tools at their command.

The broad abuses of privacy by the NSA demonstrate why those restraints are needed.