Earlier quoted context omitted.
Why just marijuana? Why not every drug? In fact, why is possession of anything a crime? We already have laws about improper storage of hazardous materials. Possession of anything should be legal. Now distribution and sale is a trickier subject but pretty easy as well. As long as you don't misrepresent what you're selling, it should be legal as well. If we are for a small government, we have to walk the walk.
Should possession of 100 lbs of weapons grade uranium be a crime?
Not that I know much about these things but from a distance I don't think possession should be a crime even in this case. Of course, you need to follow proper procedure to store it.
I am more concerned with where they obtained the said material, who supplied it to them, who produced it and so on.