Borders define geographic boundaries of political entities or legal jurisdictions, such as governments, statesorsubnational 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 crossing points.
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 In modern times the concept of a marchland has been replaced by that of the clearly defined and demarcated border.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.
In order to cross borders, the presentation of passports and visas or other appropriate forms of identity document is required by some legal orders. To stay or work within a country's borders aliens (foreign persons) may need special immigration documents or permits that authorise them to do so.
Moving goods across a border often requires the payment of excise tax, often collected by customs officials. Animals (and occasionally humans) moving across borders may need to go into quarantine to prevent the spread of exotic or infectious diseases. Most countries prohibit carrying illegal drugs or endangered animals across their borders. Moving goods, animals or people illegally across a border, without declaring them, seeking permission, or deliberately evading official inspection constitutes smuggling.
The presence of borders often fosters certain economic features or anomalies. Wherever two jurisdictions come into contact, special economic opportunities arise for border trade. Smuggling provides a classic case; contrariwise, a border region may flourish on the provision of excise or of import–export services — legal or quasi-legal, corrupt or corruption-free. Different regulations on either side of a border may encourage services to position themselves at or near that border: thus the provision of pornography, of prostitution, of alcohol and/or of narcotics may cluster around borders, city limits, county lines, ports and airports. In a more planned and official context, Special Economic Zones (SEZs) often tend to cluster near borders or ports.
Human economic traffic across borders (apart from kidnapping), may involve mass commuting between workplaces and residential settlements. The removal of internal barriers to commerce, as in France after the French Revolution or in Europe since the 1940s, de-emphasises border-based economic activity and fosters free trade.
Political borders have a variety of meanings for those whom they affect. Many borders in the world have checkpoints where border control agents inspect those crossing the boundary.
In much of Europe, such controls were abolished by the Schengen Agreement and subsequent European Union legislation. Since the Treaty of Amsterdam, the competence to pass laws on crossing internal and external boders within the European Union and the associated Schengen States (Iceland, Norway, Switzerland, and Liechtenstein) lies exclusively within the jurisdiction of the European Union, except where states have used a specific right to opt-out (United Kingdom and Ireland, which maintain a common travel area amongst themselves). For details, see Schengen Agreement.
The United States has notably increased measures taken in border control on the Canada–United States border and the United States–Mexico border during its War on Terrorism. Some have called the 3600-km (2000-mile) US-Mexico border, "the world's longest boundary between a First World and Third World country."[1]
Historic borders such as the Great Wall of China, the Maginot Line, and Hadrian's Wall have played a great many roles and been marked in different ways. While the stone walls, the Great Wall of China and the Roman Hadrian's Wall in Britain had military functions, the entirety of the Roman borders were very porous, a policy which encouraged Roman economic activity with its neighbors[2]. On the other hand, a border like the Maginot Line was entirely military and was meant to prevent any access in what was to be World War IItoFrance by its neighbor, Germany.
The following pictures show in how many different ways international and regional borders can be closed off, monitored, at least marked as such, or simply unremarkable.
