Well it isn't unprecedented, especially not anymore. For one they could technically fly in Iceland but with the ash in the air it was dangerous to do so. While

Well it isn't unprecedented, especially not anymore. For one they could technically fly in Iceland but with the ash in the air it was dangerous to do so. While people were certainly annoyed nobody tried to call it a crime or denied its necessity. In practice it is more "Send them to their home country's embassy and it is their nation's job to take them back safely. They'll likely be a bit cross but if they mess up and infect themselves repatriating without proper quarantine procedures you can't blame us."