«Best Buy is required by law to report the discovery of
certain illegal material to law enforcement, but being paid by authorities to do so would violate company policy.
Likewise, because transactions in the blockchain can have an arbitrary type of data attached, and the blockchain is immutable (unchangeable)-- i.e. its complete history is preserved forever on every computer and can not be altered, as explained in the blockchain post, it is possible to send along information that's deemed
illegal in
certain countries — pedophilia, pirated
material, government secrets... This would make the medium containing this
illegal information (the blockchain itself)
illegal to use.