Lex sanguinis (the "law of blood", also called jus sanguinis) refers to the acquisition of nationality or citizenship of a state by birth to a parent who is a national or citizen of that state. Citizenship acquired by means of lex sanguinis is not normally automatically passed on by means of lex sanguinis. This is to avoid the creation of generations of overseas citizens with no real connection with the state, but still being able to claim rights such as immigration and protection from that state.
In many European countries, lex sanguinis has been the preferred means of passing on citizenship. This has been criticised on the grounds that it can lead to generations of people living their whole lives in the state without being citizens of it. More recently these countries have begun to move more towards use of lex solis, partially under the influence of the European Convention on Nationality.