They can blacklist Bitcoins, reverse transactions and penalise people choosing to use a client other than their own. Sound like a central authority to me.
Your really under the wrong impression on how it all works.
lets say the govt tells the devs to make a client that blacklists coins, they publish it and say "this is the official client you must use it".
1. Nobody is required to use it, and anyone with half a brain wont.
2. Everyone will be yelling about how crazy it is and to not use it.
3. Someone will be forking the official client(probably the devs themselves over TOR) to include the latest updates
without that bit of code in it.
That example applies to the other two examples you mention. And let me just cut you off before you try to make your next point. "But the devs DID reverse many transactions!" No they didnt. If memory serves... there was an issue where the blockchain forked from an update, unintentionally. you either let it run its course and fix itself (screwing people in the process) or ... get the pool operators together to go back to the previous version of the client to fix it faster. The fallout was minimal and it was the right choice to make. The problem that caused it was in the original database the clients used, a bug.
If people wernt in agreement with what was done they would have left the pools rather then migrating to them.
If you want the rest of the details im sure there is a thread about it somewhere, including a chat log.