Topic of Research Paper

I have decided to research the Hemp industry and why it continues to be illegal to grow in the United States.  I feel this issue is multi-dimensional and that I could learn a great deal.  Investigating the logic behind the different arguments against the legalization is what intrigues me.  Are they sound? What is the vested interest that the government has in keeping this product illegal to grow? Are they afraid it’s a slippery slope to drug use if we grow it in the states? I feel this will be an interesting topic.