In his book, "Kitaab ut-Tawheed", Shaykh Saalih al-Fawzaan writes (pp. 49-50):

Chapter: The Ruling Upon the One Who Judges by Other Than What Allaah Has Revealed

Allaah the Most High said, "And whosoever does not judge by what Allaah has revealed, such are the Kafirun" (Al-Ma'idah 5:44). This noble verse shows that ruling by other than what Allaah has revealed is kufr (disbelief). This kufr can sometimes be the major disbelief which expels from the religion and sometimes it can be the minor disbelief which does not expel from the religion. And this is based upon the state and condition of the ruler.

So if he believes that ruling by what Allaah has revealed is not obligatory and that he has a choice in the matter, or if he belittles the rule of Allaah and believes that the Secular Laws and legislative codes are better than it, and that the it is not suitable for this era, or if he sought to please the disbelievers and the hypocrites by ruling by other than what Allaah has revealed, then all of this is the major disbelief . However, if he believed in the obligation to rule by what Allaah has revealed and knew what the judgement was in this instance, but he turned away from it while acknowledging that he is deserving of punishment, then he is a sinner and is labelled a kaafir with the minor form of disbelief. And if he was ignorant of the judgement of Allaah concerning it while having striven hard and expended efforts in knowing the judgement but erred, then he will receive a reward for his ijtihaad and his error will be forgiven. This is in relation to a particular matter (Sharh at-Tahaawiyyah pp. 363-364.

As for making judgement in matters in general (al-hukm ul-aam), then this varies.

Shaikh ul-Islaam Ibn Taymiyyah said,

For if the ruler is pious, but he makes a judgement without knowledge, then he will be amongst the inhabitants of Hellfire. And if he knew (the judgement) but he judged in opposition to the truth which he knew, he will be amongst the inhabitants of the Hellfire. And when he judged without knowledge or justice, then it is more befitting that he should be amongst the inhabitants of Hellfire. This is when he makes a judgement concerning an affair in relation to a particular person. As for when he makes a general ruling regarding the religion of the Muslims and makes truth into falsehood, falsehood into truth, sunnah into bid'ah and bid'ah into sunnah, the ma'roof into munkar and the munkar into ma'roof, forbids what Allaah and His Messenger have commanded and orders what Allaah and His Messenger have prohibited. Then this is another manifestation, the Lord of all the Worlds, Diety of the Messengers and the Master of the Day of Judgement, to whom belongs praise in this world and the hereafter will pass judgement over it. "His is the Decision, and to Him you (all) shall be returned". (Al-Qasas 28:88) "He it is Who has sent His Messenger (Muhammad) with guidance and the religion of truth (Islaam), that He may make it (Islaam) superior over all religions. And All-Sufficient is Allaah as a Witness." (Al-Fath 48:28).

He (Shaikh ul-Islaam) also said (Minhaj us-Sunnah 5/130):

There is no doubt that the one who does not believe in the obligation to rule by what Allaah has revealed is a disbeliever. Hence, whoever declares it permissible to judge amongst the people with what he considers to be justice, without following what Allaah has revealed, then he is a disbeliever. There is no nation except that it orders ruling with justice. And sometimes justice, as perceived by its senior leaders, can exist in its religion. Many of those who ascribe themselves to Islaam judge by their customs which Allaah has not revealed, such as the ancestral customs of the bedouins. And the chiefs (umaraa) were obeyed (in this) and they used to consider that it is desirable to judge by these such customs, without the Book and the Sunnah. And this is disbelief. For many people have accepted Islaam but along with this they do not judge except by their natural [inherited] customs, those which are ordered by those whom they obey. So if they know that it is not permissible to judge except by what Allaah has revealed and did not adhere to that, but in fact declared it to be lawful (istahalloo) for themselves to judge in opposition to what Allaah has revealed, then they are disbelievers.

And Shaikh Muhammad bin Ibraaheem said,

As for what has been said regarding it, that it is the lesser disbelief (kufr doona kufr) when he judged to someone other than Allaah (or something other than what Allaah has revealed) while believing that he is disobedient and that the judgement of Allaah is the truth, then this is something that occurs from him once or something like that (i.e. occurs infrequently or intermittently). As for the one who lays down laws in an organised and arranged manner and requests submission and compliance to them, then this is disbelief, even if he says, "We have erred, and the Shari'ah laws are more just", so this is disbelief that expels from the religion.

So he distinguished between the partial judgement (by other than what Allaah has revealed) which does not recur and between the general law which becomes a reference point in all of the rulings or most of them. And he affirmed that this disbelief expels from the religion absolutely. This is because the one who removed the Islamic Shari'ah and put Secular Law in its place, in replacement of it, then this indicates that he considers that this [secular] law is better and more beneficial than the Sharee'ah, and there is no doubt that this is the major disbelief which expels from the religion.

Shaykh Saalih al-Fawzaan's Clarification on the Above

The people of Takfir and Khurooj utilized the above in order to make Takfir of the rulers and so this was posed to the Shaykh and the following discussion took place (audio file here).

Questioner:

Someone has understood from your words in Kitaab ut-Tawheed, which are from your comments, with regards to the issue of al-Haakimiyyah and ruling by other than what Allaah has revealed. So they have understood from them that [by the act alone] you perform specific Takfir of a specific ruler who does not judge by what Allaah has revealed. And then they applied (what they understood from your words) to the rulers of the Gulf states.

Shaikh al-Fawzan:

[Laughs], is it due to hawaa (desire)?... the words are clear, there is no ambiguity in them, the words are clear. The distinction (tafsil) that is mentioned (i.e. previously in the beginning of the chapter) relates to them. And it was then said after that that the one who banishes the Shariżah entirely and puts another law in its place, that this indicates that he views the [secular] law to be better than the Shareeżah, and whoever holds this opinion, he is the one who is a kaafir [emphasis given]. This is in the same book itself... however they only take [from the book] according to their own understanding of it and what is of benefit to them, yet they abandon the rest of the words. If they had read the words from the beginning, the matter would have become clear [to them].

Questioner:

And the statement of Shaikh Muhammad Ibn Ibraheem is [understood] in the same way?

Shaikh al-Fawzan:

Yes, it is the same. His words mean that the one who abolishes the Shari'ah and puts in its place another law, then this indicates that he considers this law to be better than the Shareeżah. And [subsequently] whoever considers this law to be better than the Shareeżah, then such a one is a kaafir in the view of everybody, there is no doubt in this.

Questioner:

They mean the rulers of the Gulf states O Shaikh?

Shaikh al-Fawzan:

[words unclear] ... the words [in the book] are general. As for people and specific individuals, then this requires investigation.

Questioner:

So there is a difference between [takfir of] a specific individual and a general ruling?

Shaikh al-Fawzan:

Yes, between a general ruling.

Questioner:

So you intended only a general ruling [not a ruling upon specific individuals]?

Shaikh al-Fawzan:

Yes, a general ruling, there is no doubt about this. So he said "the rulers of the Gulf states (was meant)?"

Questioner:

Yes, this is it, however al-hawaa (desire) overtook him?

Shaikh al-Fawzan:

Yes, hawaa (desire)... [words unclear]... Is this rectification? Performing Takfir of the rulers of the Gulf states, is this from rectification (of the affairs)?

Questioner:

No it is not...

Shaikh al-Fawzan:

It is not rectification... it is but kindling of tribulation (fitnah).

Questioner:

May Allaah reward you...

End of the discussion. Download audio here.

Note: Refer also to this article:

• Shaykh Hammaad al-Ansaaree, Shaykh Saalih al-Fawzaan, Shaykh Abdul-Azeez ar-Raajihee on the Saudi State And Its Dissenters - (see here)