World of Warcraft executive producer J. Allen Brack has finally commented publicly on the closure of pirate WoW server Nostalrius.

"Our silence on this subject definitely doesn't reflect our level of engagement and passion around this topic," he said in a forum post.

Brack said the company had not seen a "clear legal path to protect Blizzard's IP and grant an operating license to a pirate server."

"Failure to protect against intellectual property infringement would damage Blizzard’s rights," he explained.

"This applies to anything that uses WoW’s IP, including unofficial servers."

Nostalrius, which ran a pirated version of the MMO's original 2006 "vanilla" release code and reportedly served 150,000 users, was forced to shut down earlier this month thanks to legal threats from Blizzard.

However, Brack added that Blizzard has considered running its own vanilla servers.

"We have been discussing classic servers for years - it's a topic every BlizzCon - and especially over the past few weeks," he said, although he also cited "tremendous operational challenges" in doing so.

He described a "pristine realm" that the company had considered, which deactivated all levelling acceleration, specifically "character transfers, heirloom gear, character boosts, Recruit-A-Friend bonuses, WoW Token, and access to cross realm zones, as well as group finder."

"We aren't sure whether this version of a clean slate is something that would appeal to the community and it's still an open topic of discussion."

Brack said the publisher had been in touch with Nostalrius' administrators and would hold "more conversations with them in the coming weeks."