If President Obama really wants to end the bulk collection of Americans’ telephone records, he doesn’t need to ask the permission of Congress, as he said on Tuesday he would do. He can just end it himself, immediately.

That’s what Senator Patrick Leahy, the chairman of the Judiciary Committee, urged him to do. “The president could end bulk collection once and for all on Friday by not seeking reauthorization of this program,” Mr. Leahy said.

Ending bulk collection now wouldn’t undermine Mr. Obama’s proposal to Congress. In fact, if his promise is matched by the final details (which are not yet available), it could be an important and positive break from the widespread invasion of privacy secretly practiced by the National Security Agency for years. Getting a law to create strong judicial oversight of data collection would be a check on the ambitions of future presidents. But once the question is tossed into the maelstrom of Congress, where one party routinely opposes anything the president wants, the limits could be delayed, or diluted, or just killed.

And while lawmakers wring their hands, the invasion of privacy will continue.

As Charlie Savage reported in The Times on Tuesday, the president is planning to ask Congress to end the N.S.A.’s systematic collection of telephone records begun under President George W. Bush, an action already endorsed by his independent board of advisers. The records will be left in the hands of the phone companies, where they belong, until the N.S.A. gets permission from a judge to review an individual record because of a possible tie to terrorism. (The companies would only have to store the data 18 months, compared with the agency’s five years.)