(CNN) -- It's about to get more difficult to move between smartphone carriers and still keep your existing phone.
Smartphones purchased after Saturday can't be legally unlocked without permission from the carrier, according to a recent ruling by the Library of Congress.
Congress passed the Digital Millennium Copyright Act in 1998, making it illegal to access copyrighted content and break digital rights management technologies. The software that locks a smartphone to one carrier is covered by the act, and unlocking a phone is the process of freeing a device so that it can be used with a different wireless carrier.
The Library of Congress has the ability to grant exemptions to the Digital Millennium Copyright Act, which it has done in the past for smartphone users who wished to unlock their phones. That changed with the most recent group of exemptions that went into effect October 28, but the switch included a 90-day grace period that ends Saturday, as TechNewsDaily pointed out.
The new policy only applies to new locked phones purchased after Saturday, meaning it will still be legal to unlock phones purchased before January 26 without permission.
One way to get around the requirement is to buy a full-priced unlocked phone that doesn't have a contract, but doing so adds hundreds of dollars to the phone's price tag. Carriers subsidize the costs of smartphones to draw new customers in with contracts, usually for two years, and then make back the money from monthly voice and data bills.
In its latest ruling, the Library of Congress decided the software on a phone is only licensed to the end user, meaning they don't own it, so therefore the software is not covered by fair-use rules.
Groups that lobbied to keep the exemption argued that making unlocking illegal is anti-competitive and could result in costlier phones and more electronic waste since some consumers would have to buy a new device to switch carriers.
But the final ruling says there are more options now for obtaining an unlocked phone than in previous years. Many phones are available unlocked for full price, and carriers do have policies in place for unlocking phones. Currently the rules vary from carrier to carrier.
For example, AT&T will unlock an iPhone for current or past customers as long as all contracts have been fulfilled. And Verizon's iPhone 5 is usable on AT&T's network.
However, it's unclear whether carriers will tighten these rules about unlocked phones in the future.