NEW YORK — Congress passed a bill Friday that makes it legal to “unlock” cellphones so the devices can —at least in some instances — be used on other carriers.

The law, which President Obama said he looks forward to signing, undoes a move by the Librarian of Congress in 2012. That made it a copyright violation to unlock a phone without the carrier’s permission.

The law makes it legal to unlock phones for personal use, at least until the Librarian’s next round of rulemaking, next year. The measure was passed earlier by the Senate.

Unlocking typically involves entering codes on the phone. In more difficult cases, the phone needs to be hooked up to a computer to have new software installed.

Carriers have sued people who made a business out of unlocking phones and reselling them, but individuals have not been pursued.

Carriers have become more lenient. Verizon, for instance, ships most of its phones unlocked. However, technical differences mean that it’s often difficult to move a phone to another network.