Puerto 80, the Spanish company that owns the Rojadirecta sporting website, has asked a federal judge to dismiss the government's forfeiture of its domain names. Calling the seizure "an unprecedented effort to expand both copyright liability and the reaches of civil forfeiture law," the firm argued that only direct infringement, not linking to infringing content, could be the basis for a domain name seizure.

The brief was co-authored by the prominent copyright scholar Mark Lemley of Stanford University and was filed on Friday. It claims that Puerto 80 is—at most—guilty only of assisting the infringement of others, which copyright law calls secondary liability. But, the brief argues, secondary infringement can only lead to civil, not criminal, liability. And only criminal infringement can justify the forfeiture of the Rojadirecta domain names.

We asked New York Law School copyright scholar James Grimmelmann to assess Puerto 80's arguments. He told Ars that Puerto is clearly right that linking to infringing material does not constitute direct copyright infringement. But he was less sure of the other arguments.

For example, the brief argues that criminal offenses must be spelled out in the text of a statute, not in judge-made common law. And it argues that secondary liability doctrines fall into the latter category. But Grimmelmann said that's not so clear. The relevant statute gives copyright holders the exclusive right to "authorize" others to use the work, and the courts have interpreted this as the basis for secondary liability rules. Grimmelmann said he wasn't aware of any precedents on whether there could be criminal liability for secondary infringement, calling it "a fair and open question."

The government could also charge Puerto 80 with aiding and abetting the infringing activities of their users, although Puerto 80 claims the government failed to bring such a charge in its original complaint. Also, the company argues that the forfeiture law the government is using doesn't allow seizures for aiding and abetting others' property.

The outcome of the case could have broad implications for other domain seizures. Many of the seizures we've covered, such as the case of Richard O'Dwyer and TVShack.net, targeted "linking" sites that have not engaged in direct copyright infringement. If courts endorse Puerto 80's legal arguments, it would call into question the legitimacy of all such seizures.