What is the ruling on a guest leading the residents in prayer, given the prohibition against that, and some people's citing as evidence the Prophet's (peace be upon him) leading the people in prayer on the Day of the Conquest of Mecca while he was a visitor?

The owner of the house and the imam of the mosque have a greater right to lead the prayer. If they permit a visitor or a traveler, it is permissible for the latter to lead them. This is supported by the hadith of Abu Mas'ud: "A man should not lead another man in prayer in his domain except with his permission," and the hadith of Utban ibn Malik, where the Prophet, peace and blessings be upon him, led him in prayer in his house. The permissibility of a traveler leading residents is indicated by the fact that the Prophet, peace and blessings be upon him, used to pray two rak'ahs during travel, and those behind him would complete their prayer. The hadith "Whoever visits a people should not lead them in prayer" is interpreted as referring to leading without the permission of the house owner, or that it is preferable for the visitor to forgo leading the prayer even if permitted, as the phrase "with his permission" indicates permissibility.