Net overseer Icann has asked a US court to stop an attempt to seize the web space of Iran, Syria and North Korea.
The attempt to seize the .ir, .sy and .kp domains is being made by families of victims of terrorism.
Once seized, the domains would be used to compensate victims who have already been awarded damages in a US court almost a decade ago.
In its filing, Icann said any seizure would render the domains worthless and thus provide no compensation.
The attempt to grab the domains is part of a court case begun by the families of four Americans injured in a suicide bombing in Jerusalem in 1997 for which Hamas claimed responsibility.
The families sued Iran because of its support for Hamas and sought compensation through the courts for the injuries their relatives sustained.
The group won its case by default because Iran did not turn up to defend itself and in 2003 it was awarded $109m (£65m) in damages. Since 2003, the group has been trying to take control of Iranian assets known to reside in the US in an attempt to collect that cash.
The group has enjoyed limited success over the past decade and its bid to grab the domains is the last item on its list of Iranian assets. It is not clear why it is also keen to gain control of the North Korean and Syrian domains.
The suffixes are known as "country code top-level domains" and almost every nation on Earth has one from which hang all the domains for websites run from those territories.
Icann has filed a motion with the US district court in Columbia asking for the seizure bid to be "quashed" despite the organisation's "great sympathy" for the underlying claim made by group.
Icann, or the Internet Corporation for Assigned Names and Numbers, oversees the running of the net's addressing system.
It said transferring the domains to the family group would be "largely self-defeating" as it would destroy any value they had.
The value inherent in the .ir and the other domains derives from their use and through the many companies, individuals, government agencies, organisations and others that run a website using one of the suffixes.
Handing over the domains "would simply destroy a resource utilised by the internet community" said the court papers.
Icann added that even if the court authorised the seizure it had no technical means by which to transfer the running of the respective domain systems to the family group.