Border control

[2] States and rulers have always regarded the ability to determine who enters or remains in their territories as a key test of their sovereignty, but prior to World War I, border controls were only sporadically implemented.

Border controls were in place to ensure that only people who paid their zakah (for Muslims) or jizya (for dhimmis) taxes could travel freely between different regions of the Caliphate; thus, the bara'a receipt was a "basic passport".

[17] Decolonisation during the twentieth century saw the emergence of mass emigration from nations in the Global South, thus leading former colonial occupiers to introduce stricter border controls.

In 2020, the British government under Boris Johnson announced a programme under which BN(O)s would have leave to remain in the UK with rights to work and study for five years, after which they may apply for settled status.

[25][26] BN(O)s and their dependents who arrived in the UK before the new immigration route became available were granted "Leave Outside the Rules" at the discretion of the Border Force to remain in the country for up to six months as a temporary measure.

[39] The imposition of border controls has curtailed the spread of the virus, but because they were first implemented after community spread was established in multiple countries in different regions of the world, they produced only a modest reduction in the total number of people infected[40] These strict border controls economic harm to the tourism industry through lost income and social harm to people who were unable to travel for family matters or other reasons.

Maritime border control measures are controversial in the context of international trade disputes, as was the case following France's detention of British fishermen in October 2021 in the aftermath of Brexit[47][48] or when the Indonesian navy detained the crew of the Seven Seas Conqueress alleging that the vessel was unlawfully fishing within Indonesian territorial waters while the Singaporean government claimed the vessel was in Singaporean waters near Pedra Branca.

As part of their air and maritime border control policies, most countries restrict or regulate the ability of foreign airlines and vessels to transport of goods or passengers between sea ports and airports in their jurisdiction, known as cabotage.

[p] Many countries implement air defence identification zones (ADIZs) requiring aircraft approaching within a specified distance of its airspace to contact or seek prior authorisation from its military or transport authorities.

The most common category of biosecurity policies are quarantine measures adopted to counteract the spread of disease and, when applied as a component of border control, focus primarily on mitigating the entry of infected individuals, plants, or animals into a country.

[65] Other aspects of biosecurity related to border control include mandatory vaccination policies for inbound travellers and measures to curtail the risk posed by bioterrorism or invasive species.

In 1847 the privy council ordered all arrivals with a clean bill of health from the Black Sea and the Levant to be admitted, provided there had been no case of plague during the voyage and afterwards, the practice of quarantine was discontinued.

A variety of other countries require travellers who have visited areas where Yellow Fever is endemic to present a certificate in order to clear border checkpoints as a means of preventing the spread of the disease.

Prior to the emergence of COVID-19, Yellow Fever was the primary human disease subjected to de facto vaccine passport measures by border control authorities around the world.

[76] A study in Science found that travel restrictions could delay the initial arrival of COVID-19 in a country, but that they produced only modest overall effects unless combined with domestic infection prevention and control measures to considerably reduce transmissions.

In many countries, border controls for arriving passengers at many international airports and some road crossings are separated into red and green channels in order to prioritise customs enforcement.

A similar problem exists east of the Pacific, and has resulted in countries such as Mexico and the United States tightening border control in response to the northward flow of illegal substances from regions such as Colombia.

Furthermore, the same companies are also often involved in the arms trade and thus profit twice: first from fuelling the conflicts, repression and human rights abuses that have led refugees to flee their homes and later from intercepting them along their migration routes.

The walls at Melilla and at Ceuta on Spain's border with Morocco are designed to curtail the ability of refugees and migrants to enter the European Union via the two Spanish cities on the Moroccan coast.

Over the first two decades of the 21st century, the Republican Party adopted an increasingly nativist platform, advocating against sanctuary cities and in favour of building a wall with Mexico and reducing the number of immigrants permitted to settle in the country.

Islamophobic policies such as the travel ban targeted primarily at Muslim-majority countries also feature prominently in attempts to create a hostile environment for immigrants perceived by populists as not belonging to the predominant WASP culture in the United States.

[193][194] Nationals of most countries[ac] can obtain a limited area visa upon arrival in these regions, which permit them to stay within these cities without proceeding further into other parts of mainland China.

In essence, the denial of social services outside an individual's registered area of residence functions as an internal border control measure geared toward dissuading migration within the mainland.

On 31 December 2020, Spain and the United Kingdom reached an agreement in principle under which Gibraltar would join the Schengen Area,[207] clearing the way for the European Union and the UK to start formal negotiations on the matter.

The Northern Ireland Protocol is intended to protect the EU single market, while avoiding imposition of a 'hard border' that might incite a recurrence of conflict and destabilise the relative peace that has held since the end of the Troubles.

[223] While Israeli Supreme Court has deemed the measures acceptable for security reasons, Haaretz's Amira Hass argues this policy defies one of the principles of the Oslo Accords, which states that Gaza and the West Bank constitute a single geographic unit.

As a result, there are no immigration checks between the two, but travellers arriving in Puerto Rico or the American mainland directly from the Virgin Islands are subject to border control for customs inspection.

As a consequence of awkward border situations created by the fall of the Soviet Union, certain former members of the USSR and their neighbours maintain special visa exemption policies for travellers transiting across international boundaries between two points in a single country.

[303] Similarly, since April 2017, nationals of Bangladesh, Pakistan, Sudan, Syria, Yemen, and Iran have been banned from entering the parts of eastern Libya under the control of the Tobruk government.

Official designations, division of responsibilities, and command structures of these organisations vary considerably and some countries split border control functions across multiple agencies.