they absolutely can not do that. Yes it is a gift, but age discrimination is illegal, just because they got a windfall does not mean you can discriminate against them.

if they were to be forced back to the right seat, it would have to be as a result of the law…like changing the law to prohibit CAs over 65 but allow FOs(not happening) or require thorough cog testing for a first class medical over 60 but not a second class.