Let’s say that Gloria is in charge of the Glorian nation, and has jurisdiction over all of the mining pools within its boundaries, which sums up to be over 51% of the Bitcoin network’s hash power . Gloria doesn’t like me, so her goal is to censor all of my Bitcoin addresses and prevent me from spending any of my Bitcoin.
The blocks in Gloria’s ideal blockchain will include none of my transactions.
The most naive strategy is for Gloria to instruct all of her mining pools not to include my transactions, also known as blacklisting.
However, unless Gloria’s mining pools have 100% of the entire networks hashpower, other miners outside of her jurisdiction will eventually include my transactions in a block.
This doesn’t fully blacklist me, and only ends up causing delays and inconveniences, although those delays and inconveniences can become significant depending on how much hashpower Gloria has.