The Jedi and their allies say as much explicitly, at every opportunity.
"The United Nations is neither a State nor a Government, and therefore does not possess any authority to recognize either a State or a Government."
As a federation of independent states, it allows individual governments to apply for membership, and leaves it up to individual members to accept or reject acknowledgment of sovereignty.
By the same token, one can reasonably assume they claim no authority to force another to join - nor to remain as members if any member wanted to leave the alliance.
The Galactic Republic, on the other hand, attempts to use military force (by way of their special police) to compel those planets wishing to end their ties to it to stay as members.
In fact, in response to this, Senate votes to create a Galactic Republic Army for the first time in history (only to have it come to light that an army had already been assembled in secret). The elected Chancellor is soon given emergency powers to facilitate more efficient action in what soon becomes all out war between the Republic and the Separatists.
As the war continues and intensifies, the Jedi begin to become uncomfortable with how much power the Senate has granted the Chancellor, and their own internal council begins acting more and more unilaterally, answering neither to the Chancellor nor the Senate. The CIA has gone rouge. Meanwhile some Senators are rumored to be corrupt (which seems to mean "supportive of the Chancellor"), while others begin meeting secretly to discuss options for actions to take in case the chancellor fails to revoke his war-time powers after the war has ended; they choose to keep this agenda secret from the Jedi as well.
"[Jedi knight] ANAKIN: I know the [Jedi] Council has grown wary of the Chancellor's power, mine also for that matter. Aren't we all working together to save the Republic? Why all this distrust?[Jedi knight] OBI-WAN: The Force grows dark, Anakin, and we are all affected by it. Be wary of your feelings."..."[Chancellor] PALPATINE: I fear the Jedi. The Council keeps pushing for more control. They're shrouded in secrecy and obsessed with maintaining their autonomy; ideals I find simply incomprehensible in a democracy.[Jedi] ANAKIN: I can assure you that the Jedi are dedicated to the values of the Republic, sir.PALPATINE: Nevertheless, their actions will speak more loudly than their words."..."OBI-WAN: (takes a deep breath) The [Jedi] Council wants you to report on all of the Chancellor's dealings. They want to know what he's up to.ANAKIN: They want me to spy on the Chancellor? That's treason!OBI-WAN: We are at war, Anakin. The Jedi Council is sworn to uphold the principles of the Republic, even if the Chancellor does not.ANAKIN: Why didn't the Council give me this assignment when we were in session?OBI-WAN: This assignment is not to be on record. The Council asked me to approach you on this personally. "..."PALPATINE: You must sense what I have come to suspect . . . the Jedi Council want control of the Republic . . . they're planning to betray me.ANAKIN: I don't think . . .
PALPATINE: Anakin, search your feelings. You know, don't you?
ANAKIN: I know they don't trust you . . .
PALPATINE: Or the Senate . . . or the Republic . . . or democracy for that matter.
ANAKIN: I have to admit my trust in them has been shaken.
PALPATINE: Why? They asked you to do something that made you feel dishonest, didn't they? "
..."ANAKIN: Sometimes, I wonder what's happening to the Jedi Order . . . I think this war is destroying the principles of the Republic.[Senator, and Anakin's wife] PADME: Have you ever considered that we may be on the wrong side?ANAKIN: (suspicious) What do you mean?PADME: What if the democracy we thought we were serving no longer exists, and the Republic has become the very evil we have been fighting to destroy?ANAKIN: I don't believe that. And you're sounding like a Separatist! "..."[Jedi] MACE WINDU: I sense a plot to destroy the Jedi. The dark side of the Force surrounds the Chancellor.[Jedi] Kl-ADI-MUNDI: If he does not give up his emergency powers after the destruction of [Separatist General] Grievous, then he should be removed from office.MACE WINDU: That could be a dangerous move ... the Jedi Council would have to take control of the Senate in order to secure a peaceful transition . . .Kl-ADI-MUNDI: . . . and replace the Congress with Senators who are not filled with greed and corruption. "
PALPATINE [the Chancellor]: I knew you could do it. Kill him. Kill him now!ANAKIN [Jedi knight]: I shouldn't . . .PALPATINE: Do it!!ANAKIN cuts off COUNT DOOKU's head.PALPATINE: You did well, Anakin. He was too dangerous to be kept alive.ANAKIN: Yes, but he was an unarmed prisoner. I shouldn't have done that, Chancellor. It's not the Jedi way. "
"[Jedi] MACE WINDU: You are under arrest, My Lord.PALPATINE: Anakin! I told you it would come to this. I was right. The Jedi are taking over...PALPATINE: He is a traitor, Anakin.MACE WlNDU: He's the traitor. Stop him!PALPATINE: Come to your senses, boy. The Jedi are in revolt. They will betray you, just as they betrayed me...PALPATINE: Help me! Don't let him kill me. I can't hold on any longer. Ahhhhhhh . . . ahhhhhhh . . . ahhhhhhh . . . ... I can't ... I give up. Help me. I am weak ... I am too weak. Don't kill me. I give up. I'm dying. I can't hold on any longer.MACE WlNDU: You Sith disease. I am going to end this once and for all.ANAKIN: You can't kill him, Master. He must stand trial.MACE WlNDU: He has too much control of the Senate and the Courts. He is too dangerous to be kept alive.PALPATINE: I'm too weak. Don't kill me. Please.ANAKIN: It is not the Jedi way . . .MACE raises his sword to kill the CHANCELLOR.ANAKIN: (continuing) He must live . . .PALPATINE: Please don't, please don't . . . "
But when Palpatine first discloses to his personal assistant and friend, Jedi Anakin Skywalker, that he is not only a member of the Sith, but their current high leader, he raises some potentially valid points which no one ever makes any effort to counter.
PALPATINE: Remember back to your early teachings, Anakin. "All those who gain power are afraid to lose it." Even the Jedi.
ANAKIN: The Jedi use their power for good.
PALPATINE: Good is a point of view, Anakin. And the Jedi point of view is not the only valid one. The Dark Lords of the Sith believe in security and justice also, yet they are considered by the Jedi to be. . .
ANAKIN: . . . evil.
PALPATINE: . . . from a Jedi's point of view. The Sith and the Jedi are similar in almost every way, including their quest for greater power. The difference between the two is the Sith are not afraid of the dark side of the Force. That is why they are more powerful.
ANAKIN: The Sith rely on their passion for their strength. They think inward, only about themselves.
PALPATINE: And the Jedi don't?
ANAKIN: The Jedi are selfless . . . they only care about others.
PALPATINE [smiles]: Or so you've been trained to believe. Why is it, then, that they have asked you to do something you feel is wrong?ANAKIN: I'm not sure it's wrong.
PALPATINE: Have they asked you to betray the Jedi code? The Constitution? A friendship? Your own values? Think. Consider their motives. Keep your mind clear of assumptions. The fear of losing power is a weakness of both the Jedi and the Sith. "
Well, it turns out they were!"PALPATINE: Anakin, if one is to understand the great mystery, one must study all its aspects, not just the dogmatic, narrow view of the Jedi. If you wish to become a complete and wise leader, you must embrace a larger view of the Force. ""ANAKIN: I am going to turn you over to the Jedi Council.PALPATINE: Of course you should. But you're not sure of their intentions, are you? What if I am right and they are plotting to take over the Republic? "
"ANAKIN: The situation is not good. The Jedi have tried to overthrow the Republic . . .PADME: I can't believe that!ANAKIN: I couldn't either at first, but it's true. I saw Master Windu attempt to assassinate the Chancellor myself. ""ANAKIN: I will not betray the Republic . . . my loyalties lie with the Chancellor and with the Senate . . . "
When you have a dogmatic ideological conviction, it is enough to make an unqualified, absolute, categorical statement like that. Obviously a military coop is morally justified if the elected leader holds the wrong religion!"ANAKIN: I should have known the Jedi were plotting to take over .OBI-WAN: From the Sith!!! Anakin, Chancellor Palpatine is evil.ANAKIN: From the Jedi point of view! From my point of view, the Jedi are evil.OBI-WAN: Well, then you are lost!
But of course, Anakin did bring "balance" to the force. The Jedi had considerable power, and it was increasing. Anakin attempted to bridge the divide between the two factions, as well as providing a bridge between the two and the senate (by being a Jedi, having direct personal ties to a Sith lord, and marrying a Senator), but the Jedi rejected that attempt, essentially exiling themselves.OBI-WAN: (continuing) . . . You were the Chosen One! It was said that you would, destroy the Sith, not join them. It was you who would bring balance to the Force, not leave it in Darkness. "