The presence of an intense gravitational field is required, prohibiting travel beyond the boundaries of a star system.

They periodically prohibit travel to Tibet for foreign nationals.

The embargo does not prohibit travel to Cuba, but rather the spending of dollars there without a special license from the Treasury Department.

It prohibits international travel by Bosnian Serb officials unless it is related to peace efforts.

Much more could have been done to reduce the impact on the population, such as prohibiting travel within and between islands.

"Why the Optherian government prohibits interstellar travel to its citizens."

Chinese regulations prohibit travel without permission in some areas.

Action to prohibit paid travel by senators, which has proved a staple of televised exposes, was never in doubt once the bill was brought up.

The park is open all year but extreme winter weather may prohibit travel.

Many big companies have prohibited nonessential travel by employees, he said, and attending career fairs does not usually qualify.