Surname law matronym from the name of a parent or parent-in-law; these possibilities are not necessarily open to native Icelanders. Reza Shah Pahlavi ordered Iranians to adopt Western style surnames in place of old Islamic names and titles during his reign. A law in Japan dating from 1896 requires a married couple to have a common surname. Most commonly it was the wife who took her husband's name. In 2011, this law was challenged as unconstitutional on gender equality grounds, but the Supreme Court of Japan upheld the law in 2015. Prussia tasked the implementation of surnames to E. T. A. Hoffmann.
Finnish name 21st-century Finland, the use of surnames follows the German model. Every person is legally obliged to have a first and last name. At most, three first names are allowed. A Finnish married couple may adopt the surname that either spouse had as non-married, in which case this name will be the surname of their children. A spouse changing his or her name may decide to "use" a double-barrelled name consisting of his or her former and current official surname. In the case where both spouses keep their names they may choose either name for their children, but all siblings must