A British man who fought against so-called Islamic State in Syria has been arrested on suspicion of terrorism offences after arriving back in the UK.
Aiden Aslin, 23, a care worker from Newark, Nottinghamshire, had been fighting with Kurdish armed units, YPG.
Mr Alsin was arrested at Manchester Airport in the early hours and was taken to a police station in Nottinghamshire for questioning.
His grandmother said he had travelled to Syria for "humanitarian reasons".
Mr Aslin has had two spells in Syria with the YPG and was also arrested by Nottinghamshire Police when he returned to the UK in 2016.
Emma Vardy, the BBC's home affairs correspondent, said the YPG was not a proscribed group in the UK and no Britons have been charged for fighting against IS with the Kurds, but the Home Office had repeatedly warned that returning fighters will face questioning.
Pam Aslin, his grandmother, told the BBC: "I am very disappointed that he is being treated like this again.
"I know he went to Syria against the advice of the government, but he went for humanitarian reasons and has not committed any crimes.
"After his time in Syria, he spent the past three months in Greece working at a refugee camp."
A Nottinghamshire Police spokeswoman told the BBC: "The 23 year old was arrested following claims he had allegedly engaged in the preparation to fight against Daesh and possessed articles for terrorist purposes in Iraq/Syria."
Dozens of western volunteers have travelled to Syria to join the Kurdish fight against IS, it has been estimated.
One fighter, Erik Konstandinos "Kosta" Scurfield, 25, from Nottingham, was killed in March 2015 in Syria.
Two other British men are also known to have died fighting in Syria with the Kurds - Dean Evans, 22, from Reading and Ryan Lock, 20, from Chichester.