a friend has asked me about the possibility of censoring Bitcoin by blocking transactions on the internet (as some websites or internet content are blocked in some countries). And I am not sure if a transaction that you make can be blocked before it reaches a node (miner). Or if it is totally impossible for something like this to happen.
In order to block a transaction, it must identified as transaction. Currently, communication between nodes is not encrypted, but it could be. Simply switching to https would make it impossible for anyone to block communication between nodes.