Below is the Kol Korah signed by the "gedoilim" banning canabis, and below that see a video of Reb Chaim z"l smelling canabis. Below that is a psak from R' Zilberman, son-in-law of R' Chaim ruling that it is 100% permitted.
A Kol Koreh has been released by multiple Charedi Rabbanim in Israel, banning medical marijuana in many situations.
The letter was published by two prominent Charedi Batei Din, the Bais Din of Rav Nissim Karelitz and Rav Shmuel Vosner.
In addition, it was signed by multiple other Israeli Rabbanim.
Here is a translation of the text:
Daas Torah Regarding Medical Cannabis
Because in recent times, there is a contingent of doctors who prescribe ‘medical marijuana’, including for mild illnesses, despite the fact that it is considered “samim” (a potent drug).
The Gedolei Yisrael have already paskened that using plants which are known as drugs is a Torah violation, regardless of the strength of the ingredients, whether light or heavy. Every type [of these drugs] is prohibited. Even using it occasionally, even one time, is completely prohibited. Using these drugs brings people to engage in more stringent sins of the Torah, and causes a person to lose his mind and abandon his Creator. In the end, it destroys one’s soul, Hashem yishm’renu.
Therefore we proclaim that even when doctors give patients “medical marijuana”, one is not permitted by halacha to take these drugs, unless it is at a minimum a safek pikuach nefesh (a possible life and death matter). One [who is in this situation] must ask a shaila from Rabbanim who have semicha from our communities, and not chalilah rely on doctors, because we are dealing with a Torah transgression.
Certainly, anyone who sells or deals [these drugs] to healthy people, is violating severe Torah prohibitions, and is considered “Machtiei Rabbim”.