Say: it is when people govern themselves by themselves without a (revealed) Book or Sunnah.
If it is said to you: “What is its ruling?”
Say: It is major Shirk (polytheism). The proof for this is Allah’s saying:
“Verily, the rule belongs to none but Allah.” [Surah Yoosuf: 40]?
Shaykh Yahyah Al-Hajooree
“Al-Mabaadee al-Mufeedah fit-Tawheedi wal-Fiqhi wal-‘Aqeedah”
Basic Principles on the Subjects of Tawheed, Fiqh and ‘Aqeedah: Points 45 and 46.
By Shaikh Yahyaa bin 'Alee Al-Hajooree
Al.IBAANAH Book Publishing.