Causes of Statelessness
One major cause of statelessness is the existence of gaps in a country's legal regime relating to nationality. Every country has a law, or laws, which establish under what circumstances one acquires nationality or can have it withdrawn. If nationality laws are not carefully written and correctly applied, some people can be excluded and left stateless. An age-old example is children found in a country who are of unknown parentage (foundlings). If nationality can only be acquired based on descent from a national, these children can be left stateless. Fortunately most nationality laws avoid this and recognize them as nationals of the state in which they are found.
Another factor that makes matters more complicated is that many people move from the countries where they were born. Unless a country of origin permits a parent to pass on nationality through family ties, then a child born in a foreign country risks becoming stateless if that country does not permit nationality based on birth in the territory alone. Finally the rules setting out who can and who cannot transmit their nationality are sometimes discriminatory. The laws in 27 countries do not let women pass on their nationality, while some countries limit citizenship to people of certain races and ethnicities.
A second important reason that statelessness occurs is the emergence of new states and changes in borders. In many cases, specific groups may be left without a nationality as a result of these changes. Even where new countries would allow nationality for all within the territory, ethnic, racial and religious minorities frequently have trouble proving their link to the country. In countries where nationality is only acquired by descent from a national (jus sanguinis), then this means that statelessness will be passed on to the next generation.
Statelessness can also be caused by a loss or deprivation of nationality. In some countries, citizens can lose their nationality simply from having lived outside their country for too long. States can also arbitrarily deprive citizens of their nationality through changes in law that leave whole populations stateless, using discriminatory criteria like ethnicity or race to define who and who does not belong to a state.