The system "allows intelligence agencies to do their work while limiting the margins for abuse", Bickford said.
It has, however, raised significant concerns about civil liberties, since it allows intelligence agencies to open any personal message or business communication.
Government examination of the records, which allows intelligence analysts to trace relationships between callers and identify possible terrorist cells, is considered less intrusive than actual eavesdropping.
The new bill, which allows intelligence agencies to tap phones and emails without seeking permission from a judge, sparked protests from rights groups who claimed it would legalise highly intrusive surveillance methods without guarantees for individual freedom and privacy.
One of the most contentious elements of the bill is that it allows intelligence services to vacuum up metadata, which would then be subject to analysis for potentially suspicious behaviour.
The new measure, signed into law by the president on Sunday, allows intelligence officials to eavesdrop without a warrant on international phone calls or e-mail messages to or from an American inside the United States, but only if they conclude that the "target" is outside this country.
