* Force everyone who wants assisted death to go through medical discussion alone with physiologists / doctors, require it to be at least 20 sessions or whatever seems enough.
* Only make it available and legal for people with chronic pain or other diseases that make life suck.
* Require several doctors to be present, that don't usually work with eachother or have any other specific connection to eachother.
* Require to let the patient "press" the button that injects the overdose or whatever method is used.
Etc etc. The point is to make the process complicated and to remove any doubt that this person in question didn't want to die. Of course, it isn't completely safe but so is life and that is kind of the point.