The move could affect hundreds, perhaps thousands of Cubans who access the Internet without authorization from their homes, using computers and Internet accounts that have been borrowed or purchased on the black market for as much as $50 for 80 hours a month.
Most Cubans do not have authorized access to the World Wide Web, although many can access international e-mail and a more limited government-controlled intranet at government jobs and schools.
Some physicians and key government officials are among the few Cubans authorized to use the Internet from home. According to the new law, those Cubans authorized to use the Internet must now seek additional approval to use the service on the nation's regular phone service, which is charged in Cuban pesos.
The decree passed late last year states that Internet service, already heavily controlled by the communist government, can be used only with a more expensive telephone service charged in U.S. dollars. The dollar service is prohibited to most Cubans and is typically used by foreign firms and individuals.
The law, known as Resolution 180/2003, states that the move is necessary to "regulate dial-up access to Internet navigation service, adopting measures that help protect against the taking of passwords, malicious acts, and the fraudulent and unauthorized use of this service."
The resolution further states that the Cuban phone company will use technical means to "detect and impede access to Internet navigation service" from ordinary phone lines.
E-net, the Internet service of the Cuban telephone company Etecsa, told customers in a Friday letter the new law would take effect late Saturday. It affects all other Internet service providers in Cuba as well.
E-net is the largest of a handful of Internet providers in Cuba all of them heavily monitored and controlled by the government.
E-net customers who do not have the dollar phone service can keep accessing the Internet with the ordinary phone service with special cards sold at Etecsa offices, the letter says.