And having just checked through the story he wasn't banned or told he could not go, the nursing home actually tried to get him on an accredited trip with the British Legion but it was full up. What the home did was report him missing when he failed to return home from a day out and were not...
If he is in a care home then I suggest those in charge believed he may have been too frail to attend. This isn't a naughty boy scenario - at 89 there are all kinds of issues from mobility to mental health this person may perceived to have problems with.