Whether sedition is always a mortal sin?

Objections

Objection 1 : It would seem that sedition is not always a mortal sin. For sedition denotes "a tumult tending to fight," according to the gloss quoted above (Article [1]). But fighting is not always a mortal sin, indeed it is sometimes just and lawful, as stated above (Question [40], Article [1]). Much more, therefore, can sedition be without a mortal sin.
Objection 2 : Further, sedition is a kind of discord, as stated above (Article [1], ad 3). Now discord can be without mortal sin, and sometimes without any sin at all. Therefore sedition can be also.
Objection 3 : Further, it is praiseworthy to deliver a multitude from a tyrannical rule. Yet this cannot easily be done without some dissension in the multitude, if one part of the multitude seeks to retain the tyrant, while the rest strive to dethrone him. Therefore there can be sedition without mortal sin.