Praise be to Allah.

Allah, may He be exalted, says (interpretation of the meanings):

“The command (or the judgement) is for none but Allah. He has commanded that you worship none but Him…” [Yoosuf 12:40]

“And say not concerning that which your tongues put forth falsely: ‘This is lawful and this is forbidden.,’ so as to invent lies against Allah. Verily, those who invent lies against Allah will never prosper.” [al-Nahl 16:116]

“Say [O Muhammad, to the polytheists]: ‘Tell me, what provision Allah has sent down to you! And you have made of it lawful and unlawful.’ Say [O Muhammad]: ‘Has Allah permitted you (to do so) or do you invent a lie against Allah?’” [Yoonus 10:59]

It is only for Allah to say what is halaal and what is haraam, because He is the Law-giver, and there is no law-giver besides Him. When we say that a given thing is haraam, or halaal, we refer to the evidence in the Book of Allah and the Sunnah of His Messenger (peace and blessings of Allah be upon him). Whatever we find is prohibited therein, we take as haraam, and whatever we find is permitted, we take as halaal. We refer to the sayings of the Sahaabah (Companions of the Prophet (peace and blessings of Allah be upon him) and the Taabi’een (the generation after the Sahaabah) – may Allah be pleased with them – and the commentaries of the Salaf (first generations of Islam) on the texts of the Quran and Sunnah, and we refer to the sayings and ijtihaad of the scholars.

It is not permissible for us to allow or prohibit however we wish. When new issues come up, if we do not find a text in the Quran or Sunnah, or in the sayings of the scholars of the salaf or the scholars of Ahl al-Sunnah wa’l-Jamaa’ah who came before us, then we have to refer to trustworthy scholars and people of understanding, as Allah commands us (interpretation of the meaning): “… so ask of those who know the Scripture…” [al-Nahl 16:43]. These are the scholars, who can do ijtihaad, examine the matter and make analogies (qiyaas) with the existing texts of Islam, taking into consideration the principles of necessity, and taking note of what is harmful to the interests of sharee’ah and what is beneficial, relying on the basic general principles of sharee’ah, such as the aayah (interpretation of the meaning), “… he allows them as lawful al-tayyibaat [(i.e., all good and lawful things as regards things, deeds, beliefs, persons, foods, etc.]…” [al-A’raaf 7:157] and the hadeeth, “There should be no harming nor reciprocating harm” (reported by Ibn Maajah, 2331), and avoiding following whims and desires. Every evil thing that is proven to be harmful is haraam, and every good and beneficial thing is halaal. If it is not known that it is either harmful or beneficial, then the general rule is that it is permissible (mubaah).

And Allah knows best.

(Source - Islam Q&A)