International refugee law is a set of rules and procedures that aims to protect persons seeking asylum and those recognized as refugees under relevant instruments. Grounded in the Universal Declaration of Human Rights adopted in 1948 by the United Nations, the two main sources of refugee law are treaty law, notably the 1951 Refugee Convention and its 1967 Protocol, and customary international law. It is critical to understand that customary international law applies to all states irrespective of whether they are parties to a convention or not. Thus, even if the United States had not been a party to the treaties on refugees, it would still be bound by the law. However, the United States has been a party to the 1951 Convention at its inception. This concept has long triggered theoretical discussions on the application and enforcement of international laws to various problems in the world. As Justice Cardozo has eloquently stated: "International law.. has at times, like the common law within states, a twilight existence during which it is hardly distinguishable from morality or justice, till at length the imprimatur of a court attests its jural quality." New Jersey v. Delaware, 291 U.S. 361, 383.
According to the 1951 Refugee Convention a refugee is a person who:
...owing to well-founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group or political opinion, is outside the country of his nationality and is unable or, owing to such fear, is unwilling to avail himself of the protection of that country; or who, not having a nationality and being outside the country of his former habitual residence as a result of such events, is unable or, owing to such fear, is unwilling to return to it.
See for more here.
Developments in international human rights law have reinforced the principle that the Convention be applied without discrimination as to sex, age, disability, sexuality, or other prohibited grounds of discrimination. A number of principles are especially important to note. First, non-discrimination: the provisions are to be applied without discrimination on any of the recognized grounds. For example, a Muslim cannot be rejected a refugee status merely based on his/her religion. Second, non-penalization: the refugees cannot be penalized for illegal entry into the country and breaching immigration laws. Hence, once a person is defined as a 'refugee' under this Convention, he/she may not be persecuted or arrested for migrating to the country. Third and more crucial, the principle of non-refoulement: a refugee cannot be returned or expelled back to his/her country against his/her will when he/she fears threats to life or freedom. Lastly, the Convention lays down basic rules on the minimum treatment of refugees: access to travel documents, access to courts, primary education, right to work, general welfare and housing rights.
The principle of non-refoulement is considered a part of the customary international law and cannot be derogated by any state. The purpose behind is clear: it is against international law norms to return a person to a zone of life-threatening danger. Conceptually, not giving a safe haven to a refugee is the same as expelling him/her, because if a refugee is mistreated by the newly founded home, that will have the effect of forcing that person to further migration, which takes us into a different concept of internally displaced persons. Internally displaced persons (IDPs) are defined in the 1998 Guiding Principles on Internal Displacement as:
“persons or groups of persons who have been forced or obliged to flee or to leave their homes or places of habitual residence, in particular as a result of or in order to avoid the effects of armed conflict, situations of generalized violence, violations of human rights or natural or human-made disasters, and who have not crossed an internationally recognized State border”.
While there are legal differences between refugees and IDPs, their treatment is still well-governed by the same principles of international law grounded in the Universal Declaration of Human Rights and other humanitarian instruments. See here the UNHCR Handbook on Protection of IDPs.
It is easy to lay out an international law on an issue, harder to enforce it. The adjudication of asylum status has been left to countries/States. The regional and international bodies do not have jurisdiction to rule on who is admitted or not admitted to the United States. However, they have jurisdiction to evaluate whether a given ruling by a national court has violated the international law. The domestic courts also have the prerogative of interpreting key terms from the international conventions.
For example, in Sale v. Haitian Ctr. Council, Inc.,509 U.S. 155 (1993),the U.S. Supreme Court held that the U.S. was not in violation of its non-refoulement obligation when it returned Haitians interdicted on the high seas because the Haitians were not within U.S. territory and therefore the non-refoulement obligation did not apply. However, the Inter-American Commission on Human Rights (IACHR) rejected this reasoning in IACHR, Report No. 51/96, Case 10.675, Haitian Centre for Human Rights(United States), 13 March 1997. The IACHR held that the U.S. had violated the petitioners’ right to seek asylum as well as their right to life, liberty and security of the person when it summarily returned interdicted Haitians – many of whom were subsequently arrested by Haitian authorities – without providing them with a meaningful opportunity to have their claims adjudicated. The IACHR also held that the U.S. had violated their right to freedom from discrimination, noting that a much more favorable policy was applied to Cubans and Nicaraguans. For more here.
From reading the international instruments on the refugee treatment, it is clear that states/countries cannot unilaterally turn their backs to the crisis of refugees from the Middle East or other hot spots in the world. It is at minimum a well-settled customary international law principle, as well as treaty-based law that refugees cannot be rejected, expelled and treated inhumanely. To what extent states/countries will follow this well-settled international law and custom is more about self-image and credibility as a nation in the international community. I have always believed that international law's expressive function is a lot more pronounced and crucial than its coercive function. States are like children, who won't be coerced into compliance, but may voluntarily behave accordingly if it has the effect of increasing approval by others and higher self-esteem. For a Theory of Expressive International Law see here.