The US Supreme Court has ruled that a law which makes it illegal to sell videos of animals being tortured, violates the right to free speech.

Chief Justice John Roberts said the law was too broad and invalid under the First Amendment, Reuters reports.

The ruling is a victory for Robert Stevens, who was sentenced to three years in prison in 2005 for making and selling videos of dog fights.

The 1999 law was intended to prevent depictions of animal cruelty.

It was adopted by the US Congress and originally aimed at limiting internet sales of "crush" videos which show women crushing small animals with high-heeled shoes

Mr Stevens has argued that the videos were intended to educate people about the pit bull breed and that he was not trying to promote illegal dog-fighting.

His conviction was the first in the US under the law.

Justice Samuel Alito, who dissented, said the harm animals suffered in dogfights was enough to sustain the law.

US Justice department lawyers have said that animal cruelty videos should not be entitled to any constitutional protection, but treated like child pornography, Reuters notes.

Chief Justice Roberts added that the law goes too far and suggested a measure limited to "crush" videos instead, AP reports.