The U.S. Supreme Court has dashed a bid by T-Mobile and AT&T to dismiss a class-action lawsuit that challenged wireless carriers' policies against unlocking mobile phones, Wired reports:

"T-Mobile and AT&T fought the lawsuit all the way to the nation's high court. The two carriers, on the GSM network, are accused of unfair business practices by locking down their phones to their service plans. Last year, Librarian of Congress James H. Billington listed cell phone unlocking as one of six new exemptions to the Digital Millennium Copyright Act, or DMCA."

The report said that in response to similar lawsuits, Verizon and Sprint, both CDMA carriers, have agreed to provide software to unlock cellphones after customers have completed their original contract, attorneys said. "That was the compromise we ended up with to get the cases settled," said California attorney Robert Bramson, one of the lawyers suing carriers T-Mobile and AT&T, in the article.

Unlocked phones let consumers move them from carrier to carrier without restriction, assuming the technology is compatible—that means Verizon and Sprint (CDMA), or AT&T and T-Mobile (GSM), but not across all four carriers. As it currently stands, today's phones generally end up as doorstops when consumers upgrade to new handsets, because they're locked to the same carrier.