WHY IS MEDICAL MARIJUANA NOT LEGAL IN ALL FIFTY STATES

The topic of my assignment that I chose is the legalization of medical marijuana in all fifty states. The main question I am focusing on is why medical marijuana is not legal in all of these states. I need the following questions answered please. This assignment needs to be at least two pages, not double spaced. I also need references. I will offer a bonus:
Consider the possible stakeholders for your research project. Who are they?
What social, political, or personal factors might influence the direction of your research?
What interest groups would be involved?
What patterns might influence the direction of your research?
What are the possible policy implications of your research?
Provide some examples of policies that might result from your research.