Ingolf Vogeler, Types of International Borders along the U.S.-Mexico Border

Open Borders

The European Union is the best know region of the world where borders are completely open between countries that signed the Schengen Agreement of 1985: no passports, visas, and border inspections are required any more, although technically national identity cards are required. The Schengen rules were absorbed into the European Union (EU) in 1999. Twenty-eight countries, including all European Union (EU) countries (except Ireland and United Kingdom), and three non-EU members (Iceland, Norway, and Switzerland) have signed the Schengen Agreement. However, only 15 countries have implemented the common border control and visa provisions (see map). Over 400 million people are now affected. With heighten security concerns and terrorist threats in Western Europe, the newest members of the EU might have to wait away before being allowed to eventually join the Schengen area (Schengen Visa Service, http://www.schengenvisa.cc, accessed 4 October 2010).

Former border check-point buildings, as in this photo on the Spain-France border, sometimes remain as relics of a time when European countries restricted their people from moving freely from one country to another.
In other former border crossings in the Schengen area, only national highway speeding signs and/or European Union signs with the country of entry are posted.
Although the open borders of Western Europe are rather uncommon officially today, most international borders today are, nevertheless, effectively open for the movement of people and goods, if technically illegal. The length, irregularity, and location in difficult physical environments makes international borders expensive to patrol and nearly impossible to seal, even when there is a will to do so.