It says in al-Mawsoo‘ah al-‘Arabiyyah al-‘Aalamiyyah:
Hemp (also known as Cannabis) is a plant that is sometimes cultivated for its strong fibres, which are obtained from the woody stems of the plant and are used in making string and various kinds of rope.
Growing hemp is banned in most countries because it is possible to obtain a psychoactive substance from it, known as marijuana or hashish. End quote.
The cannabis plant has a serious effect on the body, hence the fuqaha’ in the past and at present have stated that it is forbidden to consume it, as has also been stated by legal systems worldwide.
See also the answer to question no. 66227
The psychoactive substance in cannabis that has an effect on the brain and nervous system is that which the questioner referred to by its acronym THC, which stands for tetrahydrocannabinol.
It is known that this psychoactive substance is not present in leaves other than the flowering or fruiting tops, and it is not present in the seeds.
The military doctor Muhammad Fathi ‘Eed (may Allah guide him) said:
The cannabis plant is one of which cultivation is banned in accordance with the Single Convention on Narcotic Drugs of 1961, which was ratified by the Protocol of 1972. That is with the exception of a small quantity that a country that is signatory to the Convention may need for scientific research purposes.
The Convention clarified in clause (c) that what is meant by “cannabis” is any plant of the genus Cannabis, whether it is male or female, cultivated for the production of fibre or the production of drugs…
In the Single Convention on Narcotic Drugs it says: “Cannabis” means the flowering or fruiting tops of the cannabis plant (excluding the seeds and leaves when not accompanied by the tops) from which the resin has not been extracted, by whatever name they may be designated.
The Convention stated that this definition does not include cannabis leaves that are not attached to the tops and it does not include the seeds. End quote from Jareemat Ta‘aati al-Mukhaddiraat fi’l-Qanoon al-Muqaaran, 1/145, 146
Based on that, if the protein that is derived from the cannabis or hemp plant is taken from one of these two things – other than the flowering tops and seeds – which are in fact free of THC, then there is nothing wrong with consuming it, so long as it does not have a negative effect on the body apart from what may be caused by the psychoactive substance. This is the general condition that applies to everything that is available in the market of natural or manufactured substances that claim to benefit the body by increasing energy. We have discussed this in our answer concerning the ruling on sports energy drinks. Please see the answer to question no. 163968.
And Allah knows best.