Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.
As to what follows:
Swearing by other than Allah is from the shirk that is related to Tawhid al-Uluhiyyah, because it entails veneration of other than Allah Almighty by swearing by it; and singling out Allah for veneration is from the rights of Tawhid al-Uluhiyyah. If the one who swears by other than Allah venerates it like the veneration due to Allah Almighty, then this is major shirk that expels one from the religion by agreement of the scholars of Islam. However, if he doesn’t venerate it like the veneration due to Allah Almighty, then this is from minor shirk.
What proves this is what has been narrated from the hadith of Ibn `Umar (may Allah be pleased with him), who said that he heard the Messenger of Allah (peace be upon him) say, “Whoever swears by other than Allah has committed kufr or shirk.” [Ahmad (5352), Tirmidhi (1535) and Abu Dawud (3251)]
And in the narration of Ahmad and Abu Dawud, “…has committed shirk.”
As for ruling by other than what Allah has revealed, among it is that which disrupts Tawhid al-Rububiyyah, and among it is that which disrupts Tawhid al-Uluhiyyah. That which is related to legislation and passing laws that go contrary to Allah’s law, is considered shirk in Rububiyyah. Allah said:
“They took their rabbis and monks as lords besides Allah.” [Al-Tawbah 9:31]
As for that which is related to obedience to them in those legislations and laws that do contrary to Allah’s law, then that is shirk in Uluhiyyah. Allah said:
“Or have they other deities who have ordained for them a religion to which Allah has not consented?” [Al-Shura 42:21]
As for the ruling on that which disrupts Tawhid al-Rububiyyah and al-Uluhiyyah, then it is at varying levels; among it is that which is major shirk, such as believing in a creator besides Allah, or directing worship to other than Allah; and among it is that which is minor shirk, which is anything that is used as a means to it.
And Allah is the One who grants success.
Your brother,
Khalid bin `Abdullah al-Muslih
15 / 2 / 1425 AH