Two leading broadband providers are continuing the fight against the controversial Digital Economy Act 2010.
BT and TalkTalk have begun a new appeal over the decision to refuse their judicial review request for the anti-filesharing legislation.
Under the act, broadband providers may be required to disconnect those suspected of internet piracy.
However, BT and TalkTalk believe that the requirements of the legalisation are not only onerous, but also incompatible with EU law.
When the firms originally applied for a judicial review of the Digital Economy Act, Mr Justice Parker dismissed all but one of the five challenges in court.
However, BT and TalkTalk received permission to appeal this decision in October 2011.
The Digital Economy Act entered the statute books during the parliamentary wash-up period at the end of the Labour government in April 2010.
Critics say the bill was rushed and subject to insufficient MP scrutiny, having failed to receive a full Commons debate.