Supposedly the Commission (Syndicate board previously) rules prohibit the unauthorized removal or murder of a boss. Only the Commission can sanction such actions on pain on death.

However it looks like there's only been a few cases where the Commission either took action to get rid of a boss or carried out punishment against mobsters who got rid of their own boss.

Genovese ordered the murder and later demotion of his boss Costello. No one called Genovese on this. Anastasia got rid of his bosses the Mangano brothers and faced no Commission punishment. Gambino got rid of Anastasia; it's unclear as to whether he had formal or even informal Commission approval.
And of course Gotti got rid of Castellano without formal Commission approval. The other powerful Family on the board, the Genoveses was largely unaware of the plot. Certainly the Genovese boss did not sanction Gotti's action.

The only cases I'm aware of where there seem to have been either Commission pre-approval of the removal of a boss OR Commission revenge for an unauthorized removal of a boss were in the Commission approved hit of Carmine Galante (I know that now some people say he was just a captain but he certainly THOUGHT he was the boss), the Syndicate approval for removal of Siegel, and then the Commission approval for murder of Tony Bananas for his unsanctioned hit on Bruno. (Bananas thought he had approval but foolishly didn't doublecheck his sources rolleyes ).

So the question is, if you are a strong enough Mafiosi, is the Commission just a paper tiger? It wouldn't be fear of the Commission that would prevent you from whacking your boss so much as it might be fear of your boss.

Are there other cases where the Commission has given thumbs down to a particular boss or exacted bloody revenge on anyone ambitious enough to give his boss a sudden and permanent retirement?

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.