The effect: preventing cable operators from striking programming deals that exclude competitors.

Since the 1980's, the courts have tended to protect the right of dominant producers to use their patents to exclude competitors.

In San Francisco this week, city officials rejected a plan allowing cable companies to exclude competitors, and ordered a policy to allow competition.

The court's remedy further curtails Microsoft's ability to enter into agreements that have the effect of excluding competitors from the marketplace.

The inter-provincial combat is now focused instead on the efforts to protect local markets and exclude competitors.

This is because patents, by conferring rights to the owner to exclude competitors from the market, offer the incentive for people to study new technology.

For much of the 20th century, rail transport in Europe was dominated by national monopolies; these effectively excluded competitors from their networks.

"We want to prevent Microsoft from doing those things that exclude competitors," he added.

The verb "monopolize" refers to the process by which a company gains the ability to raise prices or exclude competitors.

"We may yet exclude competitors as a general rule," Mr. Mitchell said.