Cable television decoders themselves are not illegal and are often available for purchase in most countries. However, the act of cable descrambling is generally against the law because it allows cable subscribers to circumnavigate payment and view television channels that their cable companies did not grant them access to.
The legal position on cable hacking, which is the umbrella term for cable decoding or descrambling, varies greatly from country to country. Typically, a country's laws protects channels from uplinking from a particular country. This means that a person hacking ESPN is subject to prosecution under U.S. law, whereas the same person hacking Sky is susceptible to prosecution only under English law.