The massive increase in population flux due to globalization and the sharp increase in the numbers of refugees following World War I created a large number of stateless persons, people who were not citizens of any state. In some rare cases, laws for mass naturalization were passed. As naturalization laws had been designed to cater for the relatively few people who had voluntarily moved from one country to another (expatriates), many western democracies were not ready to naturalize large numbers of people. This included the massive influx of stateless people which followed massive denationalizations and the expulsion of ethnic minorities from newly created nation states in the first part of the 20th century, but they also included the mostly aristocratic Russians who had escaped the 1917 October Revolution and the war communism period, and then the Spanish refugees. As Hannah Arendt pointed out, internment camps became the "only nation" of such stateless people, since they were often considered "undesirable" and were stuck in an illegal situation, wherein their country had expelled them or deprived them of their nationality, while they had not been naturalized, thus living in a judicial no man's land.
Since World War II, the increase in international migrations created a new category of refugees, most of them economic refugees. For economic, political, humanitarian and pragmatic reasons, many states passed laws allowing a person to acquire their citizenship after birth, such as by marriage to a national – jus matrimonii – or by having ancestors who are nationals of that country, in order to reduce the scope of this category. However, in some countries this system still maintains a large part of the immigrated population in an illegal status, albeit with some massive regularizations, for example, in Spain by José Luis Zapatero's government and in Italy by Berlusconi's government.
The People's Republic of China gives citizenship to persons with one or two parents with Chinese nationality who have not taken residence in other countries. The country also gives citizenship to people born on its territory to stateless people who have settled there. Furthermore, individuals may apply for nationality if they have a near relative with Chinese nationality, if they have settled in China, or if they present another legitimate reason. In practice, only few people gain Chinese citizenship; as of 2010, China had only 1,448 naturalised Chinese in total.
The naturalization process starts with a written application. Applicants must submit three copies, written with a ball-point or fountain pen, to national authorities, and to provincial authorities in the Ministry of Public Security and the Public Security Bureau. Applicants must also submit original copies of a foreign passport, a residence permit, a permanent residence permit, and four two-and-a-half inch long pictures. According to the conditions outlined in the Nationality Law of the People's Republic of China, authorities may also require "any other material that the authority believes are related to the nationality application".
The Indian citizenship and nationality law and the Constitution of India provides single citizenship for the entire country. The provisions relating to citizenship at the commencement of the Constitution are contained in Articles 5 to 11 in Part II of the Constitution of India. Relevant Indian legislation is the Citizenship Act 1955, which has been amended by the Citizenship (Amendment) Act 1986, the Citizenship (Amendment) Act 1992, the Citizenship (Amendment) Act 2003, and the Citizenship (Amendment) Ordinance 2005. The Citizenship (Amendment) Act 2003 received the assent of the President of India on 7 January 2004 and came into force on 3 December 2004. The Citizenship (Amendment) Ordinance 2005 was promulgated by the President of India and came into force on 28 June 2005.