The United Kingdom is preparing to implement new rules to protect children from online pornography.

The new rules—which go into effect next month—require free porn sites to use the “AgeID” system, which verifies users are legally adults.

Here’s how it works: Users must first purchase a physical AgeID card for about $5 or register their drivers’ license’s information (or another form of legal identification), before the site allows them to view explicit content.

The idea is the children under the age of 18, who don’t have the AgeID card or legal I.D., won’t be able to view pornographic content.

Sites that don’t implement the new rules can be fined and blocked across the U.K.

The rules are a part of the country’s new “Digital Economy Act.”