Theoretically speaking, it might well be possible for the Church to examine a non-Catholic’s life and eventually canonize that person; practically speaking, though, it is not likely to happen for two reasons:
One of the primary purposes of canonization is to provide for the Catholic faithful authoritatively-recognized saints after whose examples a Catholic can safely model his own Christian journey. However praiseworthy was the life of a particular non-Catholic, and however much we may admire the good example set by that person, that person cannot provide to Catholic faithful a model of Catholic holiness, which includes service for and obedience to the Church founded by Christ for the salvation of all mankind.
The Church is unlikely to wish to annoy non-Catholic churches, ecclesial communities, and non-Christian believers by presuming to examine their spiritual heroes’ lives without their permission. It is also unlikely that non-Catholics and non-Christians would consider a Church examination and recognition to be authoritative, thereby rendering the exercise pointless.
In short, while we can admire the natural and/or supernatural virtues of non-Christians and non-Catholics, Catholics should look to those Catholics who have preceded us in the faith for examples of Christian holiness.
