The context of globalization and the European trend of free movement of people are decisive factors that have contributed to the avalanche of discourses regarding migrants’ rights and their content, relevance and implementation. The causes of both regular and irregular migration are diverse and while States are free to establish domestic administrative laws that regulate conditions for entrance in their territories in compliance with international standards, once admitted in such territory, migrants have generally the same rights as national citizens.  Exceptions to this rule exist and their causes and consequences shall be addressed in the following lines alongside with an examination of the relevant international instruments.
The “international charter of the migrant” is formed by the following documents: the ICCPR, the ICESCR, the 1990 Interactional Convention on the Protection of All Migrant Workers and Members of their Families, the two International Labour Organization Conventions – ILO Convention 97 on Migration for Employment and ILO Convention 143 on Migrant Workers. All these instruments are applicable to both regular and irregular migrants. Finally, we must add the UDHR and on a regional level- inter alia- the ECHR and the European Social Charter.
One of the causes that can lead to possible discrimination for irregular migrants is expressed by the Global Migration Group: “Too often States have addressed irregular migration solely through the lens of sovereignty, border security or law enforcement, sometimes driven by hostile domestic constituencies.” In other instances, discrimination is adjacent to government policies: the US passed in 1996 the Personal Responsibility and Work Opportunity Reconciliation Act as part of a flux of immigration reforms. This act denied Medicaid and other specific benefits to irregular migrants. 
Nevertheless, State conduct is not the only factor that generates discrimination. In some cases, international instruments themselves limit the rights of non-nationals: article 25 of the ICCPR refers to a series of political rights whose beneficiaries are “citizens”. This provision seems to be in contradiction with article 26 of the same instrument or article 14 of the ECHR that prohibit discrimination on various grounds, establishing an open list that includes the place of residence and national and social origins as grounds for discrimination. The CCPR General Comment No. 18 mentions that “the enjoyment of rights and freedoms on an equal footing, however, does not mean identical treatment in every instance” and that “article 25 guarantees certain political rights, differentiating on grounds of citizenship.” Moreover, when it comes to imposing administrative requirements for the sole purpose of enjoying certain rights- like for example employment or social security- States are entitled to do so in order to safeguard economical or taxation interests but at the same time to guarantee that people are protected against exploitation and abuses by non-state actors.
Finally, the Declaration On The Human Rights Of Individuals Who Are Not Nationals Of The Country In Which They Live (1985) establishes in its article 2 that States are free to regulate regarding entry and conditions for stay within their territories and to enact ‘’differences between nationals and aliens”. Article 5.2 of the same document appears to establish a separate category of rights of aliens that are subjected to limitations- inter alia, national security, public safety, public health- which proves once again that certain particular rights of irregular migrants were not envisioned as absolute. That is not to say that rights that benefit migrants are not universal: the right to life in the ICCPR and its non-derogation clause proves that certain rights stand on the universality stage.
However, the level of discretion that States have to ascertain limitations when implementing certain international obligations proves that at times universality has to surrender to State interest, ideology and policy. The Croatian Constitution is one example of an imprudent reservation of certain rights for its ‘’citizens’’.  Nevertheless, the power of decision regarding matters of nationality and membership to a community derives from state sovereignty.  International law provides non-citizens with most of the rights except the right to vote hold public office and cross borders at will.  Thus, it is possible to assert that these rights do not draw from the human condition but from civil and social status. In the ECHR context, article 14 does not appear to be unlimited either, as it can be observed in the Stec judgment, where the Court held that States can apply different treatment to certain groups in order to correct factual social deficiencies, enjoying thus a certain margin of appreciation that includes economical and social strategy as a definitive factor. In the context of the war on terrorism and specifically the US conduct we must mention the post 9/11 era that is marked by discriminative policies against aliens on the grounds of national security and domestic protection.
There are assorted conclusions that can be drawn from the above mentioned ideas: some rights maintain their universality character despite State conduct upon implementation while others are directly linked to citizenship in international instruments. States can under certain circumstances imply indirect discrimination in their legislation either as a matter of affirmative action or as a consequence of their sovereignty. Some political rights tend to be integrated in citizenship while other cultural or civil rights tend to be universal in the sense that they apply to everyone, everywhere. The issue of universality and its compatibility with “undocumented” citizens is thus complex and varies depending on the right and State in question.
Rodriguez, Gabriela, The Role of the United Nations Special Rapporteur on the Human Rights of Migrants, International Migration, 2000, Vol. 38 Issue 6.
 Ved P. Nanda, Domestic and International Legal Responses to Emerging Migration Issues: International migration: trends, challenges, and the need for cooperation within an international human rights framework, ILSA Journal of International & Comparative Law, 2011/04/01, Vol: 17, p355.
 Ibid, p370.
 James A. Goldston, Holes in the Rights Framework: Racial Discrimination, Citizenship, and the Rights of Noncitizens, Ethics & International Affairs (Wiley-Blackwell),2006, Vol. 20 Issue 3, p324.
 Ibid, p323.
 Ibid, p.323
 Frans Pennings, Non-Discrimination on the grounds of nationality in Social Security: What are the consequences of the accession of the EU to the ECHR?, Utrecht Law Review,2013,p120-121.