Foreign Affairs thinks tank “The Henry Jackson Society” which is interested in human rights and counter-terrorism said the British government in need to stop the British volunteers from joining “People’s Protection Units YPG”.

The organization added that YPG is considered a front for banned “Kurdistan Worker’s Party PKK” and warned those who joined it could incite terrorism in UK.

British Interior Ministry said Brits who came back after participating in armed conflicts in Syria and Iraq should expect an investigation by British police, as it expressed concerns participate in its "criminal-terror activities" or carry out "lone actor atrocities" when they returned home.

The Centre for the Response to Radicalisation and Terrorism, at the Henry Jackson Society, said the YPG was a subsidiary of the PKK, a "violent terrorist organisation" banned by the UK and the US.

Kyle Orton, a fellow at the centre, said: "Far from battling terrorism they're in effect aiding one proscribed terrorist organisation overcome another.
"The government needs to act now to prevent Britons falling into this trap.

Orton added "If they're already there and want to come back, comprehensive tests need to be put in place to prevent potentially dangerous individuals within our communities.”

Chris Scurfield, the father of Erik Scurfield, the first British man to be killed fighting against IS with the Kurds, said the report had upset families of British volunteer fighters.

He said: "We are speaking with other bereaved parents whose children also lost their lives in Syria, fighting alongside coalition forces to defeat ISIS and save the lives of civilians."

BBC correspondent Emma Vardy said “The issue of foreign fighters has become a central security and political question for the UK since the rise of so-called Islamic State.”

Vardy concluded ”British volunteers travelling to fight against IS with the Kurds have been likened to Britons in the 1930s who went to fight against fascism in the Spanish civil war”.

British authorities continually warn against going to fight for any group, but no returning fighters have yet been prosecuted specifically for joining Kurdish militia.

Unlike PKK, authorities didn’t recognise YPG as a terror organization and considered it as an ally in fight against ISIS.