In America Cannabis is only legal in a few states like Colorado and Washington state you can buy at recreational stores. WA DC it just became legal I'm fuzzy about the laws, I think folks can grow their own. Oregon you will be able to buy recreationally at a dispensary in October this year. Alaska is legal, you can grow your own and not sure when there will be cannabis stores.
There are 23 states that have medical cannabis but the rules vary from state to state. If you have a cannabis certification from your home state or country most states won't honor them, I know Nevada will but they just started selling cannabis at medical dispensaries. In Arizona I know if you have a certification and have cannabis on you and you get pulled over and cops find it, they will honor your cert long as you're not driving.
If you are asking about financing at banks for businesses that varies. We have a credit union in our local town that will help finances cannabis stores and businesses. Many banks won't do business but that is changing in some areas.
Check on the thread about cannabis news and activism kinda a politics section on FC.
EDIT
Cannabis is still considered as a bad drug by the Feds being lumped in with Heroin and Meth. Hopefully in the future that will be changed but not yet. The states are deciding for themselves. Hopefully with a new president he or she won't clamp down on cannabis. We had a couple of candidates for president that say that they will do that. A couple of the Republicans.
I live in WA state where cannabis is legal. The state wants to rake in big bucks in taxes. The state is going to heavily tax the medical too with more restrictions for medical patients. I hope the cost won't interfere with folks being able to afford to medicate. Some people are on fixed incomes. Luckily I'm still in the workforce and so is my husband.
Medical cannabis is legal in just 23 states.