This is broadly how genuine occupational requirements work. If there is a genuine requirement for the occupant of the job to be a certain sort of person (male, black, deaf, whatever) then you can require it. Broadly, that’s how it works. It does not work as something you tag onto a job description to rule out people you don’t really want (female, white, blind, whatever). It only works if it is an genuine requirement to the job.
This is, generally, not a problem for Christian ministries seeking to appoint a youth minister. After all, the general purpose of a youth minister is to proclaim and live out the gospel to the young people and seek to build them up to proclaim and live out the gospel themselves. And the general attitude of a youth minister should be that of someone taken up with Jesus. And as proclaiming and living out the gospel and being taken up with Jesus are things only a Christian can do, then it is fairly certain that this job will contain a genuine occupational requirement for the post holder to be a Christian. So when a Christian ministry goes to write a job description for a post and advertises it wherever, all they have to do, is make this explicit in the job description and the advert.
So why then when people write adverts and job descriptions, do they write it as if their is no Christian content to the post. They mention things like “doing one-to-one work”, “engaging with the local community”, “Build relationships with children, young people, and leaders” (all of which are fine and proper) but don’t mention things like “Jesus”, “the Gospel”, “Christian ministry”. And then they have the cheek to slap on the bottom of the advert “Genuine Occupational Requirement: Post-holder must be practicing Christian”.
This will not do! Don’t think you can write a job description that doesn’t mention anything profoundly Christian and get away with it because you tagged on some stuff about G.O.R. and now you’re home and dry. Not only is this legally dubious, it’s also completely foolish. Do you not want a youth minister who is taken up and defined by the gospel? Do you not want someone to live out Jesus’s teaching? Would you be happy with someone who doesn’t do praying, worshipping, and ministering? Then put it in your job description and your advert and for every candidate that applies make sure they know this.
If your job description reads as essentially secular don’t think you can make it more Christian by fiddling it so only a Christian can apply. Either it’s a Christian ministry and it’s written as such or it’s not and anyone can do it. And if that’s the case then how Christian is your ministry?