Judging by that which Allaah has revealed
Question

                Can one who judges by something other than that which Allaah has revealed be regarded as just, if he does not wrong people?
Praise be to Allah.The Muslim ummah is one nation, with one ‘aqeedah 
          (belief) and one sharee’ah (law). Because every flock needs a shepherd 
          and every nation needs a leader to guide them to goodness and ward off 
          evil from them, Islam enjoins the appointment of a ruler over the ummah, 
          who is to be elected by the Muslims, to rule them according to the Book 
          of Allaah and the Sunnah of the Messenger of Allaah   
          (peace and blessings of Allaah be upon him).  
Allaah sent His Messenger of establish the 
          laws of Allaah and to judge with truth and justice, as Allaah says (interpretation 
          of the meaning):  
“O Dawood (David)! Verily, We have placed you as a 
          successor on the earth; so judge you between men in truth (and justice) 
          and follow not your desire   for it will mislead you from the 
          path of Allaah. Verily, those who wander astray from the path of Allaah 
          (shall) have a severe torment, because they forgot the Day of Reckoning[Saad 
          38:26]  
The mission of the ruler is to rule the Muslims 
          according to the Qur’aan and Sunnah, to spread justice among the entire 
          ummah, to carry out the hudood punishments, to spread Islam, to protect 
          the ummah and to engage in jihaad for the sake of Allaah. Allaah says 
          (interpretation of the meaning):  
“Verily, Allaah commands that you should render back 
          the trusts to those, to whom they are due; and that when you judge between 
          men, you judge with justice. Verily, how excellent is the teaching which 
          He (Allaah) gives you!”[al-Nisaa’ 4:58]  
Justice is one of the most important principles 
          of Islam, which applies both to Muslims and others:  
“and let not the enmity and hatred 
          of others make you avoid justice. Be just: that is nearer to piety” 
          
[al-Maa'idah 5:8 – interpretation of the meaning]  
          
The ruler of the Muslims is responsible for 
          his flock. He has to rule them in accordance with the laws of Allaah, 
          check on their situation, and lead them to that which will bring them 
          happiness in this world and in the Hereafter. The Prophet  
          (peace and blessings of Allaah be upon him) said:  
“Each of you is a shepherd and is responsible 
          for his flock. The ruler who is (appointed) over the people is a shepherd 
          and is responsible for his flock…” (Narrated by Muslim, no. 1829)  
          
Allaah created mankind, sent down revelation 
          to them, and sent the Messengers to them to judge them by that which 
          Allaah has revealed. Whoever does not judge by that which Allaah has 
          revealed is a kaafir, as Allaah says (interpretation of the meaning):  
          
“And whosoever does not judge by what Allaah has revealed, 
          such are the Kaafiroon (i.e. disbelievers — of a lesser degree as they 
          do not act on Allaah’s Law)”[al-Maa'idah 5:44]  
If the ruler judges according to the Book 
          of Allaah and the Sunnah of His Messenger  
          (peace and blessings of Allaah be upon him), it becomes obligatory to 
          obey him and haraam to go against him or to rebel against him. Allaah 
          says (interpretation of the meaning):  
“O you who believe! Obey Allaah and obey the Messenger 
          (Muhammad), and those of you (Muslims) who are in authority. (And) if 
          you differ in anything amongst yourselves, refer it to Allaah and His 
          Messenger, if you believe in Allaah and in the Last Day. That is better 
          and more suitable for final determination”[al-Nisaa’ 4:59]  
          
If the ruler judges by something other than 
          that which Allaah has revealed, or he enjoins disobedience to Allaah, 
          then we should not hear and obey. The Prophet  
          (peace and blessings of Allaah be upon him) said:   
“The Muslim is obliged to hear and obey whether 
          he likes it or dislikes it, unless he is commanded to disobey (Allaah), 
          in which case he should not hear and obey.”(Narrated by Muslim, 1839)  
          
The ruler is entrusted with the affairs of 
          the ummah; he must rule them according to the laws of Allaah, and be 
          kind and sincere towards them. If he does not do that, then he must 
          be advised. If he does not respond (to that advice), the Muslims should 
          choose another ruler from among those who are both pious and strong.  
          
The just Muslim ruler will have great virtue 
          and an honourable status on the Day of Resurrection. The Prophet  
          (peace and blessings of Allaah be upon him) said:  
“The just will be with Allaah on thrones of 
          light on the right hand of the Most Merciful, and both His hands are 
          right hands – those who are just in their rulings and are fair with 
          their families and those of whom they are in charge.”(Narrated by Muslim, 
          1827)  
If the ruler oppresses or cheats his flock 
          and is not sincere towards them, Allaah will deprive him of Paradise. 
          The Prophet  (peace and blessings 
          of Allaah be upon him) said:  
“There is no person whom Allaah has placed 
          in charge of others, who dies whilst he is insincere towards his people, 
          but Allaah will forbid him Paradise.”(Narrated by Muslim, 142)  
          
And he  
          (peace and blessings of Allaah be upon him) said:  
“There is no Muslim ruler who is put in charge 
          of the Muslims’ affairs then he does not strive on their behalf or act 
          sincerely towards them, but he will not enter Paradise with them.” (Narrated 
          by Muslim, Kitaab al-Imaarah, 22).  
Islam is the way for all of the ummah, so 
          all of the individual members are equal in that they should – indeed 
          must – follow its guidance, act in accordance with its teachings, calling 
          call others to Islam and strive in jihaad for the sake of Islam.  
          
Allaah warns everyone who fights against the 
          religion of Allaah or fights those who speak the word of truth in the 
          houses of Allaah, that He will put them to shame in this world and punish 
          them in the Hereafter. Allaah says (interpretation of the meaning):  
          
“And who are more unjust than those who forbid that 
          Allaah’s Name be glorified and mentioned much (i.e. prayers and invocations) 
          in Allaah’s mosques and strive for their ruin? It was not fitting that 
          such should themselves enter them (Allaah’s mosques) except in fear. 
          For them there is disgrace in this world, and they will have a great 
          torment in the Hereafter[al-Baqarah 2:114]   
Everyone who entices the Muslims away from their 
          religion, persecutes them or humiliates them will be in Hell if he dies 
          without having repented. Allaah says (interpretation of the meaning):  
          
“Verily, those who put into trial 
          the believing men and believing women (by torturing them and burning 
          them), and then do not turn in repentance (to Allaah), then they will 
          have the torment of Hell, and they will have the punishment of the burning 
          Fire” 
[al-Burooj 85:10]  
Openly proclaiming the word of truth is an 
          obligation upon every Muslim at every time and in every place. Allaah 
          commanded His Messenger to proclaim the truth, and He guaranteed to 
          protect him from his enemies. Allaah said (interpretation of the meaning): 
          
“Therefore proclaim openly (Allaah’s 
          Message   Islamic Monotheism) that which you are commanded, and 
          turn away from Al‑Mushrikoon (polytheists, idolaters, and disbelievers). 
          
Truly, We will suffice you against the scoffers”[al-Hijr 
          15:94-95] 
 The greatest jihaad is to speak the 
          truth before an unjust ruler.  
In both the general and the specific sense, 
          the judge will be rewarded, if he is knowledgeable and is able to make 
          ijtihaad. If he passes a judgement and makes the right decision, he 
          will have two rewards, one for his ijtihaad and one for being right. 
          If he passes a judgement and makes a mistake, he will have one reward, 
          that for his ijtihaad. The Prophet  
          (peace and blessings of Allaah be upon him) said:  
“If the judge passes a judgement and makes 
          ijtihaad and is right, he will have two rewards. If he passes a judgement and makes ijtihaad, and makes a mistake, he will have one reward.” (Narrated by Muslim, 1716)