Last year, after it was revealed that the National Security Agency was indiscriminately scooping up records of Americans’ telephone calls under an expansive interpretation of the Patriot Act, President Obama urged the public to relax.


“Nobody is listening to your telephone calls,” he said. As for the so-called metadata that was being vacuumed up and stored by the government – the source, destination and duration of calls _ the president assured the nation that the program was free of abuses and subject to aggressive oversight.


But since then Obama has “evolved” in response to concern in Congress and the country about a repository of information that potentially could provide a window on the daily lives of millions of U.S. citizens. And last week, the administration announced a new blueprint for the collection of metadata that it wants Congress to enact into law.


The new program would address the two most common demands of critics: that massive amounts of phone data not be stored for long periods of time by a government agency, and that investigators should not be able to decide for themselves when to search the “haystack” of metadata for the “needle” of telephone numbers possibly linked to terrorist plots.


Under the new arrangement, metadata would be maintained not by the government but by the telephone companies in a format that would make it easy for investigators to “query” or search it, and the database would include records from cellphones as well as land lines. The companies would preserve the records for 18 months, compared to the five years they were kept by the NSA. Finally, Congress would make permanent an interim arrangement under which the government has agreed to seek a court order for every query (except in an emergency).


These are significant reforms, but important details remain to be clarified. For example, the White House says judicial approval for searches of metadata would be based on “national security concerns.” That’s too vague a formulation; at a minimum, new legislation must require that investigators convince a judge that there is “reasonable, articulable suspicion” that a telephone number to be run through the database is connected to terrorism.


Desirable as these reforms are, they don’t address the question of whether even a more privacy-friendly metadata program is necessary to detect terrorist plots. The same presidential advisory group that called for an end to bulk collection of metadata by the government also cast doubt on the usefulness of the program, concluding that information it yielded “was not essential to preventing attacks” and could have been obtained by other means. Perhaps a reformed metadata program is a defensible backstop to other surveillance programs, but Congress needs to scrutinize that proposition.