The duties of citizens
Armed resistance to oppression by political authority is not legitimate, unless all the following conditions are met: 1) there is certain, grave, and prolonged violation of fundamental rights; 2) all other means of redress have been exhausted; 3) such resistance will not provoke worse disorders; 4) there is well-founded hope of success; and 5) it is impossible reasonably to foresee any better solution.
Source: Catechism of the Catholic Church (Vatican.va)