Is it permissible to pray behind someone who bore arms against his Muslim people alongside the occupation army, after the declaration of armed struggle against the oppressive colonizer in Algeria?

If these individuals committed this act voluntarily, by choice, and with knowledge of its prohibition, then they have done what necessitates disbelief (kufr), based on the statement of Al-Shawkani in his exegesis of the verse: "And whoever among you takes them as allies, indeed, he is [one] of them" (Quran 5:51), meaning he is part of them and counted among them. This is a severe warning, because the sin that necessitates disbelief is one that has reached the extreme limit. Therefore, it is not permissible to pray behind them in this situation, unless they repent with a sincere repentance, in which case it is permissible to pray behind them.