There is nothing wrong with studying commerce and accounting, even if it includes haraam things such as riba and taxes, on condition that the student or teacher believes that what Allah has forbidden of such things are indeed haraam, and he is only studying these subjects in order to understand what they involve of evil and falsehood, or to benefit from whatever they involve that is not contrary to sharee‘ah, because all companies and organizations need this knowledge and can benefit from it. The same applies to studying law, to understand what it involves of falsehood and warn others about it, or to benefit from what is beneficial in it whilst disavowing what it involves of falsehood. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him) was asked about the ruling on studying man-made laws, and he replied: 

Those who study and teach (man-made) law fall into three categories: 

1.

Those who study it or teach it in order to find out its reality or to find out how the rulings of sharee‘ah are superior to it, or to benefit from it with regard to that which is not contrary to sharia, or so that he can benefit others thereby. There is nothing wrong with this from a shar‘i point of view as far as I can see; rather it may be something for which a person will be rewarded if he seeks to expose its faults and show the superiority of shar‘i rulings over it. The ruling on those who come under this heading is the same as the ruling on those who study the rulings on riba, and different kinds of alcohol and gambling, and other things such as invalid beliefs, or who teach about them so that they will be recognised and the ruling of Allah concerning them may be known, and thus he benefits others whilst believing that they are haraam, like others who study man-made laws that are contrary to the laws of Allah whilst believing that they are haraam. The ruling in this case is not the same as the ruling on one who learns witchcraft or teaches it to someone else, because witchcraft is haraam in and of itself because of what it involves of shirk and worshipping the jinn instead of Allah. So the one who learns it [witchcraft] or teaches it to someone else does not achieve that except by means of shirk, unlike the one who learns law than teaches it to others, not in order to rule by it or out of a belief that it is permissible; rather he does that for a permissible or legitimate shar‘i aim, as stated above… 

End quote from Majmoo‘ Fataawa al-Shaykh Ibn Baaz (2/231). 

For more information please see the answer to question no. 12874. 

For more information please see also the answer to question no. 103181. 

It is essential that the one who studies this subject should have knowledge of Islamic rulings, so that he will be safe from being deceived by falsehood and being influenced by what he studies of specious arguments; if he is confused by anything, he should hasten to ask the people of knowledge, so that he can distinguish truth from falsehood, right from wrong. 

It says in Fataawa al-Lajnah al-Daa’imah (14/232): It is not permissible to learn man-made law in order to implement it, so long as it is contrary to the laws of Allah, but it is permissible to study it and learn it in order to demonstrate the falseness and deviance from the truth that is involved in it, and to highlight the justice and fairness of Islam and how it is sufficient for people and achieves their interests. It is not permissible for the Muslim to study philosophy, man-made law and so on if he does not have the ability to distinguish between true and false, lest he fall prey to confusion and deviates from the straight path. But it is permissible for one who is able to study it and understand it after studying the Qur'aan and Sunnah, in order to differentiate between what is good in it and what is bad, so that truth will be known as truth and falsehood will be known as falsehood, so long as that does not distract him from things that are more obligatory according to sharee‘ah. Thus we know that it is not permissible to make the teaching of these subjects widespread in academies and institutes; rather it should be only for specialists who are qualified to do that, in order for them to undertake their Islamic duty of supporting truth and exposing falsehood. End quote. 

And Allah knows best.