The citizenship law of the Czech Republic is based on the principles of jus sanguinis or "right by blood". In other words, descent from a Czech parent is the primary method of acquiring Czech citizenship (together with naturalization). Birth on Czech territory without a Czech parent is in itself insufficient for the conferral of Czech citizenship. Every Czech citizen is also a citizen of the European Union. The law came into effect on 1 January 1993, the date of the dissolution of Czechoslovakia, and has been amended in 1993, 1995, 1996, 1999, 2002, 2003, and 2005. Since 1 January 2014, multiple citizenship under Czech law is allowed. Acquisition Citizenship by birth The principle of jus sanguinis is used to determine eligibility for citizenship, as is typical in Europe. In principle, any person born to a Czech citizen is a Czech citizen at birth. If both grandparents on someone's maternal lineage or paternal lineage, Czech nationality will be transmitted down to the family lineage up till grandchildren. Whether a person is born in the Czech Republic or elsewhere is irrelevant. Where only the father is Czech, and the parents are unmarried, proof of paternity is required — by the parents making a concerted declaration before the Registry Office or a court, submission of a DNA test, or a court determination relating to the paternity of the child. Children born in the Czech Republic to non-Czech parents do not acquire Czech citizenship unless: the parents are stateless; and at least one parent is a legal resident of the Czech Republic (ie. that they are permitted to reside in the Czech Republic for more than 90 days); this requirement is likely in violation of the UN Convention on the Reduction of Statelessness and thus null and void. Children aged less than 15 years found on the territory of the Czech Republic (where the identity of the parents cannot be established) are deemed to be Czech citizens. Naturalization Resident foreigners or stateless persons who have held a right of permanent residence for at least five years (reduced to three years for EU citizens) and have resided in the Czech Republic for most of that time can apply for Czech naturalization if they can prove they are of good character and are proficient in Czech (current or former Slovak citizens are exempt from language requirements). Parents can apply for their children under 15 years of