I’m afraid the law will not allow for pilots who reach a certain age (65?) to effectively be demoted to FO, or to be repositioned at the bottom of a seniority list, should one exist. Indeed any less favourable treatment, purely on the basis of age will by definition be clearly ‘ageist’! That is against the law. Absolutely correctly, it should not be tolerated.
However...... There are a number of Objective Justifications allowable in law, to proscribe compulsory retirement of pilots upon reaching a certain age. Not only is a compulsory retirement age legal. To many of us, it appears eminently sensible.
It doesn’t escape many’s attention that those agitating for an increase in retirement age, tend to be those coming to the latter stages of their careers. Having, for decades taken full advantage of the compulsory retirement of the cohorts of pilots before them!
Where are the legions of twenty year old pilots pushing for an extension to all of our careers?