Do countries have the right to keep people out? Most of us take the answer for granted until we try to defend it. This level sets out the strongest arguments on both sides, then the fair criticisms of each.

Sovereignty and an odd asymmetry

In international law, states generally have the right to decide who may enter and stay, limited by obligations they have accepted, such as non-refoulement. The Universal Declaration of Human Rights of 1948 says everyone may leave any country, including their own, and return to their own country. It says nothing about entering anyone else's. The result is a right to leave any country but no general right to enter another. Defenders see this as sensible; critics compare it to a right to marry with no right to find a partner.

The case for controlled borders

The philosopher Michael Walzer argued in 1983 that deciding who becomes a member is central to a community's self-determination. Without that power, he suggested, there could be no communities with a distinctive character and history of their own. Walzer was no hard-liner: he held that states owe help to refugees in desperate need and that workers admitted to labor in a country must be offered a path to citizenship.

Christopher Heath Wellman grounds border control in freedom of association. Just as an individual may decline to marry or join a club, a legitimate state may decline to associate with outsiders, though he argues it may still owe them aid. David Miller, a liberal nationalist, stresses that a shared national identity sustains the trust that democracy and the welfare state need. States, on his view, may weigh newcomers' claims against citizens' interests, while taking refugees seriously.

Other defenders make practical points. Low-wage citizens may bear the costs of competition while others enjoy the gains. Democracies, they say, should decide their own composition by consent, and laws that are not enforced erode respect for law in general.

The case for open borders

In 1987 Joseph Carens published the classic argument on the other side. He compared birthright citizenship in rich democracies to feudal class privilege: an inherited status, gained by luck of birth, that greatly shapes a person's life chances. If liberals reject inherited privilege at home, he asked, how can they defend it at the border? He added an argument from consistency: we treat freedom to move between cities as a basic liberty, so the reasons to stop it at a national border need to be strong.

Libertarians reach open borders by another road. They stress that employers, landlords and migrants have rights to make voluntary agreements, so a law that blocks a willing worker from a willing employer harms both. The philosopher Michael Huemer offered an analogy: forcibly stopping a hungry man from walking to a market where he could buy food would wrong him, even though no one owed him food. Utilitarians add the large economic gains discussed in Level 6.

Fair criticism of each

Critics of open borders reply that sudden large flows could strain housing and public services, overwhelm democratic consent and provoke a backlash that hurts migrants already present. Poor countries might lose skilled workers. And a world with open borders has never been tried at modern scale, so its effects are guesses.

Critics of controlled borders reply that the club analogy fails because a state, unlike a club, uses force against the people it excludes. The political theorist Arash Abizadeh argued that border controls coerce outsiders, so they must be justified to those outsiders as well. Others note that arguments from national culture have often slid into ethnic exclusion, as the quotas in Level 2 show, and that birthplace is morally arbitrary.

Most governments take a middle path, selecting by family ties, humanitarian need and skills. Canada introduced the first points system for selecting immigrants in 1967, scoring applicants on education, language and occupation, and Australia, New Zealand and Britain later adopted versions of it.

Points systems reflect a view that admission should serve the receiving country's needs, while family and refugee admissions reflect obligations to others. Most countries mix all three.

Worked example: a small country's choice

Imagine a prosperous island nation that receives a million applications to settle each year and has room, its government says, for one hundred thousand. Walzer would let citizens decide, but insist that refugees in dire need come first and that admitted workers be able to become citizens. Miller would weigh the national interest and social trust, while still taking a fair share of refugees. Wellman would grant the state a right to refuse, perhaps paired with a duty to send aid abroad. Carens would ask why the cap is a hundred thousand rather than much higher, and demand a reason the excluded could accept. A libertarian would ask why the state should stand between applicants and the employers and landlords willing to take them.

Notice that most of these thinkers share a premise: the excluded applicant is a person whose interests count. They disagree about how much those interests weigh against citizens' claims, which is where the real argument lies.