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International Border from WikiPedia:

Borders define geographic boundaries of political entities or legal jurisdictions, such as governments, states or subnational administrative divisions. They may foster the setting up of buffer zones. Some borders are fully or partially controlled, and may be crossed legally only at designated border checkpoints.

In the past many borders were not clearly defined lines, but were neutral zones called marchlands. This has been reflected in recent times with the neutral zones that were set up along part of Saudi Arabia's borders with Kuwait and Iraq (however, these zones no longer exist). In modern times the concept of a marchland has been replaced by that of the clearly defined and demarcated border. For the purposes of border control, airports and seaports are also classed as borders. Most countries have some form of border control to restrict or limit the movement of people, animals, plants, and goods into or out of the country. Under international law, each country is generally permitted to define the conditions which have to be met by a person to legally cross its borders by its own laws, and to prevent persons from crossing its border when this happens in violation of those laws.

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