Sky Broadband began blocking Newzbin2 on Tuesday, after receiving a court order telling it to do so.
The ISP is the second major internet provider to block access to the file-sharing website, after BT started doing so around the end of October. However, major rivals TalkTalk and Virgin Media said on Thursday that they have received no such court order themselves, and are not blocking the site.
"We have received a court order requiring us to block access to this illegal website, which we did on 13 December," Sky said in a statement. "Moving forward, as and when clear and legally robust evidence of copyright theft is presented, we will take appropriate action in respect to site blocking, which will include complying with court orders."
The European branch of the Motion Picture Association (MPA) won a court order in July that forced BT to block access to Newzbin2. The site reacted by releasing a client that can circumvent BT's Cleanfeed filtering technology.
In early November, shortly after BT began carrying out the order, the MPA sent letters to all the major ISPs, saying the organisation intended to seek similar court orders and asking whether the ISPs intended to fight against this move.
At least one of the ISPs, TalkTalk, replied to the MPA letter by saying it was unhappy with some of the terms of the proposed court order, particularly those relating to the costs of carrying out the blockage.
TalkTalk regulatory chief Andrew Heaney told ZDNet UK on Thursday that the ISP sent that reply three weeks ago, and has heard nothing from the MPA since. Similarly, Virgin Media said it has also heard nothing recently from the film studios' representatives, and had certainly received no court order.
The MPA has also gone to BT to seek a block of the Pirate Bay file-sharing website, but BT has said it will not institute further blocks without a court order for each case.
ZDNet UK has asked Orange whether it has received any rights-related court orders recently, but had not been given an answer at the time of writing.
James Firth of the Open Digital policy organisation wrote on Thursday that Sky — unlike BT — most likely blocks sites purely according to their IP address, without checking that the address is still linked to the nefarious site.
"Newzbin will — and there's strong evidence they have done already, several times — change their IP address," Firth wrote. "It is well known that IP addresses have all but run out. Nearly all IP addresses allocated are recycled — they've been in use before. Pity the website owner who picks up Newzbin's old IP address."