In 1889, Japan took its first step toward forming a modern constitutional state by promulgating the Meiji Constitution, dividing power among the legislature, or Diet, the executive branch, or Cabinet, and the judiciary, with the Supreme Court at the top.

Under the Meiji Constitution, sovereignty resided with Emperor Meiji. The courts handed down decisions on his behalf and in his name.

Under today's Constitution, promulgated in 1946 and enforced in 1947, sovereignty resides with the people and the courts exercise judicial power to secure the people's rights.