Martin O'Donnell pointed out a CNET News.com article on the lawsuit filed by the Foundation for Taxpayer and Consumer Rights alleging that AT&T Wireless, Cingular Wireless, and T-Mobile USA are thwarting FCC regulations on mobile phone number portability by maintaining electronic locks on their customers' handsets. These three carriers were chosen as defendants in the lawsuit because they run compatible networks using the GSM (Global System Mobile) standard.

According to the complaint:

Instead of having to purchase a new handset in order to use the respective defendants' services, GSM customers could use their own handsets and simply replace their SIM cards... with SIM cards from another carrier.... Moreover, since GSM is the standard throughout much of the world, frequent international travelers, for example, could buy SIM cards with prepaid minutes... to avoid the steep roaming charges imposed by their GSM carriers.

I've talked extensively on Operation Gadget about practical issues with international roaming, and how some U.S.-based GSM carriers make it difficult for customers to take use their phones economically and practically while overseas. In my opinion, T-Mobile and Cingular have relatively reasonable handset unlocking policies, while AT&T Wireless has an unreasonable unlocking policy.

I only really focus on international roaming issues because I think that it's reasonable for wireless carriers to have one or two year service contracts with customers if the carrier subsidizes the customer's handset. But, the customer should have the right to break that contract by paying a cancellation fee that is no greater than the carrier subsidy plus interest. GSM phones should be usable on any compatible network at any time.