Why do Rastafarians believe it is okay to use cannabis? Almost every denomination and sect of Christianity believes it is wrong to use cannabis. For some reason they always quote Scripture that pertains to alcohol as reasons for why one should not use it. Why do Rastafarians believe it is okay to use cannabis?
Disclaimer: I am not Rastafarian. I do not personally agree with some of the things I'm about to write, but I will try to answer the question with respect to their beliefs.
Rastafarianism is a unique sect of Christianity. They hold many Orthodox positions, but they also have a few views that many may find strange. So they're really no different than any other sect of Christianity in that aspect.
One position in particular is their view of cannabis as a &quot;sacred herb&quot;. They call cannabis &quot;Ganja&quot;, and though it is not the most important aspect of their religion, it is the one that they are usually associated with.
Most Rastafarians use cannabis strictly as a religious sacrament, believing it to be too sacred to use for recreational purposes. Some believe nothing should be held in such a high regard, so they use it for whatever purpose they deem appropriate, and some do not use it at all. One thing that they all have in common is that they believe the so-called War of Drugs is a war against people, and they quote Yeshua as a reason for why it should be put to an end:

&quot;Blessed are the peacemakers: for they shall be called the children of God.&quot; Matthew 5:9

Medicinal Purposes
One reason Rastafarians believe it is okay to use cannabis is because of its medicinal properties. They quote Revelation, which says:

&quot;In the midst of the street of it, and on either side of the river, was there the tree of life, which bare twelve manner of fruits, and yielded her fruit every month: and the leaves of the tree were for the healing of the nations.&quot; Revelation 22:2

They believe cannabis is this tree of life. Although many would believe this interpretation is a bit too far fetched, it is interesting that cannabis has shown to possess unequivalent healing properties. It was discovered in the 1990's that the human body contains what is known as the endocannabinoid system, with cannabinoid receptors in the brain and central nervous system. The name comes from the fact that these cannabinoid receptors are identical to the molecular structure of the cannabinoids present in cannabis. According to Wikipedia, the endocannabinoid system is:

Known as &quot;the body’s own cannabinoid system&quot;, the ECS is involved in a variety of physiological processes including appetite, pain-sensation, mood, and memory, and in mediating the psychoactive effects of cannabis.

Some scientist even believe that a lot of human health problems stem from what is known as a cannabinoid deficiency, and the US government actually own a patent on the cannabinoids present in cannabis- Patent 6630507.
Religious Sacrament
Most Rastafarians use cannabis as a religious sacrament. They gather together and smoke the dried buds of the cannabis plant, then accompany this with Scripture study. In this sense, cannabis is viewed as a sacramental incense (the burning of dried plant matter), similar to what the Catholics do for their religious services. They believe cannabis brings them closer to God (whom they call Jah) by healing their mind and spirit:

&quot;For so YHVH said unto me, I will take my rest, and I will consider in my dwelling place like a clear heat upon herbs, and like a cloud of dew in the heat of harvest.&quot; Isaiah 18:4

Illegality of Cannabis
Many people are surprised when they learn that cannabis is harmless and yet still illegal, especially since the Drug Enforcement Agency openly admits that there has never been a reported death as the result of cannabis consumption; but this is no shock to the Rastafarian. They believe it's illegal status is part of the prosecution against their people. The reason for this belief is because it's thought that the West (which they call Babylon) wishes to suppress people from a particular side effect- which seems to be a keen awareness of exposing things Rastafarians deem unhealthy to the soul; such as consumerism, economic exploitation, political deception, social injustice, and media brainwashing.
God Made It
If I was to agree with anything that Rastafarians believe, it would be that God made cannabis, and He gave it to us as a food, a medicine, a tool, and a blessing. To the Rastafarian, cannabis is not to be confused with alcohol, which must be fermented and manufactured. Alcohol is well known, in both the world and the Scriptures, for its devastating effects on the human mind and body (which explains why &quot;Babylon&quot; is so eager to push it on society). Cannabis grows everywhere, whether man plants a seed or not. The first chapter in the Scriptures say:

&quot;And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.
And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it [was] good.
And the evening and the morning were the third day.&quot; Genesis 1:11-13

Then...

&quot;And God said, Behold, I have given you every herb bearing seed, which is upon the face of all the earth, and every tree, in the which is the fruit of a tree yielding seed; to you it shall be for meat.
And to every beast of the earth, and to every fowl of the air, and to every thing that creepeth upon the earth, wherein there is life, I have given every green herb for meat: and it was so.
And God saw every thing that he had made, and, behold, it [was] very good. And the evening and the morning were the sixth day.&quot; Genesis 1:29-31

Other verses include:

&quot;He causeth the grass to grow for the cattle, and herb for the service of man.&quot; Psalm 104:14

And...

&quot;Better is a dinner of herbs where love is, than a stalled ox and hatred therewith.&quot; Proverbs 15:17

And...

But he answered and said, Every plant, which my heavenly Father hath not planted, shall be rooted up.
Let them alone: they be blind leaders of the blind. And if the blind lead the blind, both shall fall into the ditch.
Then answered Peter and said unto him, Declare unto us this parable.
And Jesus said, Are ye also yet without understanding?
Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught?
But those things which proceed out of the mouth come forth from the heart; and they defile the man.
For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
These are the things which defile a man: but to eat with unwashen hands defileth not a man.&quot; Matthew 15:13:20

Conclusion
I'll conclude this with a quote from a popular Rastafarian philosopher:

“Herb, herb is a plant. I mean herbs are good for everything. Why, why these people who want to do so much good for everyone, who call themselves governments and this and that. Why them say you must not use the herb?...Them just say, ‘no, you mustn’t use it, you mustn’t use it because it will make you rebel.’ Against what?”- Bob Marley

...One Love :)