Not a scholar of Kant or Fichte, so not sure what they in particular would have to say about that.
But the overall problem is one of moral authority. The thing is there is an ambiguity when it comes to "right" (or "Recht") between a legal code of conduct and a "correct" or "ethical" way of doing things.
Now from the perspective of the law makers, these two things are likely one and the same. The law is codified morality, so what the law say IS, by definition, "correct" and "ethical" and thus legally binding not just by force.
So it's not just that there is a legal restriction of "Thou shalt not rebel". It's the underlying assumption that "Violating the law is just if and only if the law is unjust" is a nonsense sentence, because the law can, by definition, never be unjust. It's what justice and the judiciary system is build upon.
So if you argue that the law is unjust, that isn't just a point of critique of a provision, it's a challenge to the entire system, because YOU demand the authority to define what is "right" or "wrong" in opposition to an entity that has already made a claim to that power. Seriously you'd define a novel form of morality outside of the legal system. And without any violence THAT in itself is a revolutionary thought.
So what is the morality of a revolution? From the perspective of a ruler/lawmaker a revolution can NEVER be just. The laws are in place for a reason and justice is defined as following the law, so there can be no exception to the law except for within the law itself. So it's not that a revolution is illegal because it is prohibited, it's rather that the idea of a just revolution would make the legal system unjust and an unjust justice system would be an intrinsic contradiction, that cannot exist. Either it would accept it's competitor and reform or it would "unjustify"/criminalize and persecute them. But either way the revolt would be rendered "unjust".
On the other hand from the perspective of the rebel, the system is the one being unjust. However how do you draw the demarcation line between a just rebellion and an ordinary criminal who faces the same disconnect between a personal morality and a legal ethics and where you'd often side with the law?
Between a just revolution and a power grab towards tyranny and might makes right?
And suppose we can define a just revolution, wouldn't a just constitution have to acknowledge that and how would it be supposed to do that given that this would be near self-defeating it's own purpose of being just.
Just as a side note, the German constitution actually has such a weird provision in Article 20 Paragraph 4:
(4) All Germans shall have the right to resist any person seeking to abolish this constitutional order if no other remedy is available.
So there is a law that allows to break the law if the law breaks the law. (Let that rest for a second)
Also for obvious reasons legal experts have already conjecture that this is more of manifestation of intent as any legislative and executive power could either abolish that law or argue it doesn't apply in this particular case, so it's a right without much impact.
But isn't such statement actually self-evident? If the legislation contains unjust laws, or those who hold power apply it unjustly, isn't it right to fight them and establish a better government? What's the point of considering it a problem?
Yes it's trivial that it's appropriate to rebel against unjust laws, the non-trivial part, as explained, is what that means and who decides that.
The point here is that according to Fichte humans have a natural tendency to expand and improve, and so whenever a political institution tries to hold them, there is a risk that they will eventually rebel making such institution "explode". Hence, it is not possible to expect a nation not to rebel whenever oppressed by a constitution or a government, making the rebellion law unjust. I don't know anything about Fichte or idealism, but his solution seems a bit forced to me (or maybe it is just a natural consequence of his philosophical system?). Is that right?
Would be great if you could give the source material for that quote or indeed Fichte's quote to that extend, because I'd read that differently. From a physical point of view the gas in a balloon won't make it explode unless you change the exterior conditions. Like decreasing the volume of the balloon while keeping the volume of gas the same, pumping more gas into a steady volume of balloon or by increasing the energy of the gas molecules, in the balloon, by heating the system.
However that doesn't mean that things would be steady without these changes, far from it. The gas in a balloon is continuously in motion and molecules collide with each other and the walls and distort the shape of the balloon or change its direction. However the nature of a balloon is that the "walls" aren't rigid, if a molecule bounces into a wall, it dents the wall just a little bit and then bounces off. The wall will then oscillate because of that dent but ultimately will come back to it's resting position. And if the dent is large enough (by multiple molecules or much force of one), it will change the balloons direction but the shape of the balloon will still come back to a resting position.
So the shell of the balloon is both rigid with respect to small disturbances and malleable with respect to large ones. An explosion of the balloon only happens if either one particle is so fast that the pressure on a small area of the balloon can no longer hold it inside, so that it tears a whole into the wall or if the balloon is compressed or hindered it it's movement so that the pressure inside gets so high that it tears apart the entire balloon.
So the picture doesn't necessarily mean a continuous breaking of the system through progress but could very well advocate for reforms in order to avoid breaking the system.