Then by all means light up..
I've been 'lighting up' for almost 45 years, and I've been asking this same question for that same amount of time.
I have yet to get a rational answer...
OK rational answer...God instructed Adam and Eve not to eat from one tree, everything else was ok. But Eve went ahead and ate one anyway and convinced Adam it was ok, just because The Serpent told Eve not to worry, that it was ok. Of course God found out. Now, God is law of the land and has created a perfect world. Now with law comes rules to follow by and consequences to face when law is broken. Adam and Eve broke God's law and the consequence is evil and death has been brought into the world. Hence, there are two kinds of sin, original and actual. Original you are born into (thanks to Adam and Eve) actual sins you commit willingly.
Marijuana thus far is not legal with the exception in some states as medicinal.
So if you are smoking marijuana just to be smoking it illegally. Well then if you get caught you face consequences. But there is a chance for law to change. Such as God has changed his law of all of us to avoid damnation.
The sin Adam and Eve brought into the world, death is our punishment. Well God decided to change that. When he sent his son Jesus Christ to die on the cross, he did it to wipe away our sins. So come judgement day we could live in a perfect world. Now the catch is we are saved by faith and grace. If you truly believe in your heart Jesus died for our sins, you shall be saved.
Now if the law of the land decides to legalize Marijuana, the catch will probably that you will have to pay taxes on it.