Starlink's satellite network is registered with the UN's International Telecommunication Union (ITU) through Norway, with the US listed as an associated administration. That makes both governments legally responsible for preventing unauthorized transmissions.
Since 2023, the ITU's Radio Regulations Board has repeatedly "strongly urge[d]" Norway and the US to have SpaceX "immediately disable unauthorized transmissions" in Iran. SpaceX can switch off terminals in any country, but neither government has made it do so.