I would recommend that you do not ride while high.
As others have mentioned, you probably can find a closed course or road-path-trail with no vehicle and no pedestrian traffic, but your impairment likely will significantly elevate your risk if there are any curves, challenging areas, or small road defects or path/trail defects such as small potholes or fallen debris like small twigs, pinestraw, leaves, etc... Your reaction time and your critical thinking and observation capability will be severely diminished. You're probably more likely to be too late to miss the pothole ahead, and perhaps lose control where your body hits the pavement and a wrist or clavicle gets broken, if not an arm, a leg or a knee injury also.
Willie Nelson & Snoop Dogg likely have a much better health plan than you do. They won't have any problems accessing the world's best orthopaedic surgeons and physical therapists. Willie and Snoop also would not worry about the $60,000+ bill for Life-Flight Helicopter Air Ambulance for transport to the nearest trauma center in a worst case situation. I'm just saying that your Super-Platinum Comprehensive Health Plan is probably among the best there is, but often there are limits and certain exclusions....................oh well great, you got Aflac too, coverage doesn't fill out every possibilty no matter what their mascot duck and bama football guy leads you to believe.
Now, what if you are stupid enough to bike stoned in an area with pedestrians, dog walkers, and other casual but sober riders enjoying the path/trail, and you cause or are involved in a collision with someone or another rider where injuries are sustained to the other party/parties. You're gonna be in deep ship, except substitute the fourth letter in the alphabet that comes after p , for that fourth letter in the word ship. The lawyers involved are going to cite "contributory negligence" and that you were reckless in your willfull decision to ride while impaired. It won't make a difference if the other party stupidily jumped directly into your path......
Don't be a dumbass. There are already enough idiots that engage in such beyond dumbass behavior. My neighbor is a trauma surgeon, and he often sees the victims of preventable beyond stupid behavior by such dumbasses. He also sees the many dumbasses that manage to only hurt themselves during their high stupidity. Sometimes such events are life changing in causing disabilities, and sometimes such events can be life ending...................................all because of what?? because you wanna ride high!..............................Grow up and act like a responsible adult. Don't promote such stupid behavior!!! Remember that others may read this now and in the future. You may have the intellectual maturity and critical thinking to pose a question such as you have done here, but heck who the heck knows, as someone's 11 year old grandson might read this and determine that Oh Yeah The BikeForums Debate on Riding While High is that it is Okay and There Is No Risk.
Hey, we are all old, but I do not think it benefits anyone to share stories of acts of stupidity when we may have been less intelligent , in a public forum such as this.
You certainly don't wanna give some benchmark that those that are now young dumb and stupid will try to emulate and exceed.