In today's society, a child born to unmarried parents are not subject to the same poor treatment or lack of legal rights that they once faced. However, some nationality laws tend to discriminate against children born to unmarried parents, mainly in regards to Jus Sanguinis. Jus Sanguinis is a policy that dictates that citizenship of an individual is determined by parental citizenship status.
Many European countries prefer this method of determining citizenship. This method recognizes maternal blood as the basis for determining citizenship. The child's paternity dictates their nationality through if the child is legitimate. If the child is born to unmarried parents, that child is supposed to be a citizen of the same country as the mother. Any child that is born to unmarried parents will have an extremely difficult time gaining citizenship to their father's country if they are able to at all.
Many countries followed the rule of Jus Soli, or "right of soil" until the late 18th Century. Canada and the United States continue to follow this rule, which grants citizenship based on place of birth instead of parental citizenship. The law of soil allows for one to have no other connections to the country besides birthplace to achieve citizenship.
A parent's birthplace is unimportant. Acknowledgment of paternity is not important. It does not matter if both or neither of the parents happen to be citizens of the United States. The United States does not recognize right of blood as a way of determining citizenship.
Most European countries began using blood right to determine citizenship in the late 18th Century and have been using it since. Many countries combine the rules of right of blood and right of soil.
Laws regarding the treatment of children born to unmarried parents has changed drastically within the last century. However, nationality laws that base citizenship on right of blood still treat children born to unmarried parents differently than legitimate children. The rule of blood holds the paternity of the child in the highest regard.