[wideawake]

In the early fifteenth century there were once three claimants to the papal office and each had his adherents. Were those who denied the authority of the other two claimants schismatic? No.

This is a very poor analogy.

The antipopes of this time all claimed legitimate election by different factions of the College of Cardinals. They had, weak or strong, juridical claims.

Derksen is saying that Pope John Paul II was indeed elected by the College of Cardinals, but that by promulgating a Code of Canon Law that Derksen personally dislikes he invalidated his own election.

This is a novel claim and not at all analogous to the factionalism of the 1400s.

[ultima ratio]

I am not saying Derkson is right; I am saying he is in good faith. Nor is it merely a matter of the College of Cardinals' electing somebody as you suggest; it is a question of whether obvious heretical beliefs de-legitimize a real pope and whether JPII fits into this category.