WASHINGTON—Americans should be able to take their used cellphones and tablets freely from one wireless carrier to another if they aren't under contract, the White House said Monday, offering the latest victory to Internet activists seeking to shape U.S. technology policy.

Wireless companies have long sold cellphones at discounted prices in exchange for long-term service agreements. The catch: Consumers can't easily take what would otherwise be an expensive smartphone to a rival carrier who offers a better price while the phone is under contract.

Tech-savvy users have used computer programs as a workaround to unlock their phones. But last fall, the Library of Congress, which has oversight of certain copyright matters, banned the practice if a carrier doesn't give permission, saying cellphones should no longer be exempted from a section of copyright law. The move went into effect in January, prompting a backlash from activists who flooded a petition on the White House's website.

By the time the White House responded Monday, the "Make Unlocking Cell Phones Legal" petition at the White House's website had garnered more than 114,300 digital signatures.

"Consumers should be able to unlock their cellphones without risking criminal or other penalties," R. David Edelman, an Obama administration adviser on Internet and privacy issues, said in the official response to the petition. He called the position "common sense" and "crucial for protecting consumer choice."