January 1, 1948
Italy’s new post-war constitution takes effect. Starting on this day (according to the Interior and Foreign Ministry legal interpretations), Italian mothers could pass Italian citizenship to their children independently of the father. Sons and daughters born or adopted* prior to this day had to have an Italian father in order to acquire Italian citizenship jure sanguinis (unless the father was unknown).
CAUTION: Do not look at the date of birth of the parent when considering this rule. Look at the date of birth of the child (next in line, of either gender) then consider the gender of that child’s parent. It’s perfectly fine for Italian mothers to be born before 1948 as long as their children (male or female) are born January 1, 1948 or later. (And see below about Italian courts.)
Also, prior to this day, one way an Italian woman lost her Italian citizenship was when she married a foreign husband and that country granted citizenship to her automatically as a result of marriage. (The U.S., for example, granted automatic citizenship to non-American women marrying American men until the Cable Act which went into effect on September 22, 1922.) Starting on January 1, 1948, an Italian woman could never lose her Italian citizenship solely as a result of marrying a foreign man. (She had to take some other, separate action, such as naturalization, to lose her citizenship.)
Italian authorities improperly applied this part of the 1948 constitution for many years. A woman who lost her Italian citizenship solely because she married a foreign man can immediately reclaim Italian citizenship by making a simple declaration at a local consulate. Her descendants (born on or after January 1, 1948) only retain their Italian citizenship if the marriage to a foreigner occurred on or after January 1, 1948.
Example: Paulina, an Italian citizen, emigrated to the United States in 1938 and never naturalized. She married a U.S. citizen in 1944, but the U.S. stopped granting foreign women automatic citizenship through marriage in 1922. Paulina had two children: Alice, born in 1946, and George, born in 1948. George was born an Italian citizen, but Alice was not (according to Interior Ministry legal interpretations).
Fighting a 1948 Case in Court. Note that, starting in 2009, many plaintiffs have won cases in Italian courts arguing that the 1948 constitution was retroactive and applied to all women, including Italian citizen-mothers who had given birth to children before 1948. Consequently these plaintiffs have been able to win citizenship recognition through older maternal ancestries than the Interior Ministry and Ministry of Foreign Affairs currently accept.