Hi, Sunshine.
I am not an attorney, social worker or psychologist... just putting that out there to make it clear I am not giving professional advice. However, in my job I do see divorce agreements and custody evaluations. When one spouse accuses the other of having a substance problem (current or history) I have seen judges order substance abuse evaluations for both parties (so of course that means a waste of money for the spouse who does not have a history of this problem). This will result in a report by a psychologist assessing the individuals' risk of having/continuing a substance abuse problem. If a spouse has a recent history of substance abuse but is now clean, I have seen judges order that spouse to submit to monthly drug testing at their physician's office to be sent to a lab, the result of the labs go to the physician as well as to the psychologist &/or the court, and if the test is clean, the individual has another month of parenting time; if the test is dirty, no parenting time (and presumably other consequences?). If a spouse is new to recovery, the court may mandate supervised visitation or may allow limited visitation (such as a weeknight dinner with the child/ren or a visit of several hours on a weekend day but without an overnight component).
Again, I'm not a professional. I'm only sharing information I've come across in my job.