ANO's are all very well and good, but crew have neither the training nor equipment to determine if anyone is acting under the influence of alcohol / drugs.
The only personnel so trained and equipped are medical professionals / police officers.
Caution is required before off-loading and/or accusing pax of alcohol / drug induced misbehaviour.
Negotiation with the pax may result in a voluntary off-load which is a much better result. This has worked for me in the past.
I have no sympathy for the miscreants by the way.