New Delhi, July 17 -- TOKYO - Princess Aiko turned 26 last December, completed a university degree, and has quietly assumed royal duties alongside her father, Emperor Naruhito. She will never inherit his throne. Japan's parliament made that definitive on Friday, passing the first amendment to the Imperial House Law since 1949 without removing the ban on female emperors - a decision that contradicts what surveys show a large majority of the Japanese public actually wants.

The amendments, approved by the National Diet, take a different approach to the dynasty's shrinking succession problem. Under the revised rules, male relatives from distant branches of the imperial family can now be adopted into the line of succession provided they are o...