What realistically can the crew do ? There was an incident at MAN last month when the crew refused to open the door upon arrival until the Police arrived due to an individual refusing to wear a mask. The Police initially refused to attend (Which tells you a lot) and when they did - 40mins after arrival, the crew were warned that they cannot hold passengers as it is classed as false imprisoment.
Crew of the airline have now been advised to simply log the incident and to not challeng the individual.