Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Cannabis is forbidden according to the Muslim scholars. So anybody who says that it is lawful is mistaken and his opinion has no weight in Sharia because it goes against the Sharia evidence that states that everything that causes drunkenness is forbidden.
Actually this herb was mentioned by Muslim scholars in the past. Ibn Hajar al-Haitemy mentioned it in his book: “Al-Fatawa al-Kubra”.
He reported from Ibn al-Baytar that he said: ‘The kind of cannabis which I saw was only in Egypt where they grow it in the fields and which is very intoxicating. So, when the person eats a little bit of it he gets drunk. Some people used it and it caused them to lose their sense and it can even cause death’ .
So, it is forbidden.
Allah knows best.