I have already answered this somewhere in some comments or posts on my Facebook. Anyway, you used the words ‘uprising against a kafir leader’ – Having a non Muslim leader is unacceptable for Muslims, it is not allowed in the shariah for a non Muslim to be in authority over Muslims. However how do we remove or change the situation is the question that really should be asked and not are we allowed. We are allowed as long as we are able to fulfill the conditions of removing him.
Firstly, we need to establish why are we uprising or rebelling is it because we have no jobs? We have little food? We are being treated unjustly? Or is it because we want Allah law sharia to judge us and be implemented in our lands. If it is the former then the uprising will be fruitless, we may achieve some of our goals but gain terrible other problems in the process and the end will be one tyrannical rule for another. If it is the latter then we know we will achieve our goals and the end will be safety and peace and happiness.
Secondly, if we have the correct intention and reason to upraise we need to examine the citizens, and people who are uprising are they people who love zina, wine drinking, commit shirk worship graves and awliyaa, engrossed in bidda and deviation, defenders and callers of democracy, socialism, liberals or women’s rights. If it transpires the citizens are mainly of the above then the uprising and removing of this disbelieving leader will not bring about the desired outcome as mentioned in point one above. We should concentrate on dawah fixing the people beliefs, religion and uprightness. If it transpires the citizens are none or very little of the above then we have completed one of the pre requisites of removing a disbelieving leader.
Thirdly, if we have fulfilled the two conditions above we need to look for a third and that is will greater harm come to the Muslims if we remove this disbelieving leader? Greater harm according to the salaf is one handful of Muslim blood being spilled. When Ibn Umar was asked by some companions and tabeein to take the pledge of allegiance and fight Yazeed he refused saying “I do not want one handful of blood spilled on my account” Muslim blood is more sacred than the kaba Ibnu Maaja narrates from Abdullah ibnu ‘Umar who said; “I saw he messenger of Allah (s) by the Ka’aba saying: “how good you and your scent are, how great you, and your sanctuary is. By he whose hand my soul is in, the violation of a believers rights is greater in the sight of Allah than yours, (from his rights are) his wealth his blood and that you do not think of him except in a good light.” Ibn Masood narrates that the messenger (s) said: “the first to face trial amongst the people will be those who spilled blood.” (Bukhari and Muslim). So we need to establish which is greater the spilling of a Muslim blood or the injustice we face from this disbelieving ruler. If it transpires we can remove him without the spilling of blood then we need to fulfill another condition.
Fourthly, if the above three conditions are met we then need to establish do we have a replacement for this disbelieving leader? Are we united upon this new leader or are we going to fight each other afterwards spilling blood because each group wants his leader to rule. If we do not have a replacement in place who is pious, will judge by shariah, everyone is united upon him, we have opened ourselves to possible further disunity and killings. If we say we will have democratic elections and decide….. then do I need to say anymore? If we say it doesn’t matter just remove this one and we will put our trust in Allah then this is not correct as Allah has ordered us to take our precautions and be wise.
As for the current situation in Syria it is different now from when it was at the beginning. All the above I mentioned was applicable at the beginning, but when the situation changed to millions being displaced, losing their homes and their families being killed and raped and a civil war between sunni and shia. In such a situation these Syrian people have no choice but to fight back and remove this tyrant and disbeliever, we can only hope and pray Allah gives them victory and someone better than Bashar. This is now a jihad and no longer a rebellion or uprising.