During the Tang Dynasty, the "Palace Domestic Service" was established north of the imperial palace, opposite the "Central Secretariat" located to the south, hence the terms "Southern Office" and "Northern Office."
During the reign of Emperor Wenzong of the Tang Dynasty, eunuchs wielded immense power, controlling not only the military but also the "Northern Bureau," where they held great authority. They manipulated the emperor, protected their allies, intimidated officials, and ran rampant across the land with utter lawlessness. Anyone with a shred of righteousness was deeply distressed and outraged by this.
Emperor Wenzong of Tang, eager to break free from political stagnation, issued an edict in the second year of the Taihe era calling for virtuous and outspoken scholars to submit memorials "pointing out the flaws in governance," promising to appoint them based on merit. A Jinshi scholar named Liu from Youzhou seized this opportunity, submitting a memorial that directly accused powerful clans and corrupt officials of defying the law due to a fractured legal system. He argued that because the Southern and Northern Courts were established separately for civil officials and eunuchs, a criminal in the south could escape to the north, and while the outer court sought to enforce justice, the inner court could grant exceptions, declaring, "When laws issue from multiple sources, the people are left without direction... the law differs between the inner and outer courts."
The imperial advisors Feng Su and Jia Ji, tasked with reviewing submissions, were deeply impressed by Liu's insight and courage. However, fearing retaliation from the powerful eunuchs, they dared not recommend his work to the emperor, instead selecting only twenty-three mediocre memorials to submit.
Later, the idiom "laws from many doors" came to describe inconsistency in making or enforcing legal rules.
Source: *New Book of Tang*, "Biography of Liu"
Meaning of the Idiom: Later, the Chinese idiom "法出多门" came to describe inconsistency in making or enforcing legal rules.