Halakhah do Jozuego 7:11

A sinner who violated the decrees of the community, if they were not excommunicated, they are counted in a quorum of ten and they are obligated in all of the mitzvot. For thus it is said of Achan, "Israel has sinned"(Joshua 7:11) even though he sinned, he is still Israel. Therefore, they still maintain their holiness and they are not removed from the generality of Israel who are not suspected for their oaths. However, if they have been excommunicated, since they must separate themselves from the community of the diaspora, if they were to include them, what would be left of their curse what good was their decree? It is not appropriate to include them at all for they have already separated them from their community.