Mozilla is resisting an attempt from the Department of Homeland Security (DHS) to force it to remove an add-on called MafiaaFire Redirector.
When a website has been taken down and replaced with a new one, MafiaaFire automatically redirects users to the new site. But because this frequently happens when a site has been closed down by the government, the DHS wants Mozilla to stop helping users find the new sites.
"The ICE Homeland Security Investigations unit alleged that the add-on circumvented a seizure order DHS had obtained against a number of domain names," says Mozilla lawyer Harvey Anderson.
"Here the seized domain names allegedly were used to stream content protected by copyrights of professional sports franchises and other media concerns."
But Mozilla isn't taking it lying down. The company wants answers to a number of questions - first and foremost whether any courts have ever determined that Mafiaafire is illegal in any way (they haven't).
The company is also querying whether it's legally obliged to disable the add-on, and says it wants to see a seizure order.
Anderson says he's concerned that domain seizures are already leading to censorship and threatening the open internet, citing a recent case in which over 80,000 websites were taken down by Immigration and Customs Enforcement (ICE) when only ten were actually offering child porn.
"In this case, the underlying justification arises from content holders' legitimate desire to combat piracy," he says.
"The problem stems from the use of these government powers in service of private content holders when it can have unintended and harmful consequences."