Fox Broadcasting, having lost a key court ruling last month, is more eager than ever to kick Dish Network's new ad-skipping Hopper DVR off the market.

Last month, a federal judge found that Dish's DVRs probably don't break copyright law, ruling that the Hoppers can stay on the market and operate normally while Fox proceeds with its lawsuit. Fox is arguing that it can't wait, and it says that Dish's product has the potential to do serious damage to various aspects of the ad-supported TV business. As promised, it appealed the lower court decision and has now filed its opening brief at the US Court of Appeals for the 9th Circuit (PDF via Deadline.com).

The various affiliates of the Fox media empire originally filed the lawsuit back in May.

"Dish's unauthorized, commercial-free VOD service is anything but fair, and the need to enjoin it could not be greater," Fox lawyers write in their new brief. "PTAT [Prime Time Any Time] and AutoHop cut the legs out from under the ad-supported broadcast television business model, devalue Fox's commercial air time in the eyes of advertisers, [and] block Fox's own advertising efforts."

Under a Fox contract, Dish can only provide video-on-demand (VOD) services if it disables any kind of fast-forwarding features. Dish's PTAT service is being "openly market[ed] as commercial-free VOD," in violation of that agreement, write Fox lawyers.

Fox argues the judge's decision fails to seriously analyze the four "fair use" factors, and relies on a "strained" reading of the key Cablevision ruling, which allowed for remote DVR services. The idea that its users, not Dish, are in control of what data gets copied is much too lax, says Fox: "Under this standard, any infringing service can now escape direct liability as long as its customers 'press a button' to sign up."

Changes made by Dish since launching the product "provide the illusion of user 'control' when in fact Dish still runs the show." The DVR's default settings still record all four networks every night of the week and save that programming for eight days, Fox notes.

However much Fox might be in a hurry, its failure to win an injunction in the lower court means it will have to wait at least a little while longer with Dish's product on the market. The appeals case won't be fully briefed by the end of next month; Dish's brief is due January 17, and Fox can then file a reply to that brief before January 31.