Maintaining Islam and Islamic values depends on the existence of powerful Islamic sovereignty. Islamic sovereignty should be protected so that the five interests of the Islamic society i.e. intellect, religion, life, property and honor are not jeopardized. Verse nine of chapter Hujarat is one of the verses of the Qur'ān which refers to the necessity of peace in the Islamic society and the maintenance of security and Islamic sovereignty. Studying the concept of Baghy in this verse, this paper seeks to address this question: Revolt against what kind of ruler, what kind of revolt, and under what conditions is considered as Baghy? Reflecting on the traditions of the infallible Imams and the verses of the Holy Qur'an, especially the mentioned verse that is the most important origin of this concept, the results of the paper show that "Baghy" does not exclusively mean revolt against an infallible Imam, but includes revolt against a just ruler and Imam as well. Revolt against a tyrant is not a right and accepted kind of Baghy, since it is not basically considered Baghy at all. Moreover, an action is considered as Baghy in which the doer is a Muslim not a non-Muslim. Baghy is done in group, not individually; it is armed and violent, not peaceful, and the intention of rebels for revolt against the infallible or just Imam is proved.