There are many patients who are using medical cannabis to alleviate some of the symptoms of Parkinson's. In a number of countries smoking cannabis or taking cannabis drops administered under the tongue, purely for medicinal purposes, is legal. Cannabis in no way can replace any of the regular Parkinson's medications available on the market today, but as additional assistance, for some patients it does relieve an amount of pain, stiffness, rigidity which in turn leads to a better night's sleep. I think we can all agree that achieving a good six hour's uninterrupted sleep in bed at night , one can better cope with Parkinson's during the day.
If you would like to read more about medical cannabis, here is a link to a very interesting article supporting the claims of many Parkinson's patients who have benefited from what once was a simple medicinal herb originally used in traditional Chinese medicine dating back to 2737 BCE. In 1906 things changed when the U.S. Government introduced the "Pure Food and Drug Act" which in turn created the "Food and Drug Administration" that we refer to now as the FDA.