Anthony Cheng, who works for Chinese state broadcaster CCTV, was detained at Bangkok’s Suvarnabhumi airport Monday night on his way to report in the war-torn Iraqi city of Mosul where troops are battling the Islamic State group.

Gas masks and ballistic vests, which are frequently used by reporters around the world, are classified as war weapons in Thailand and require a licence.

Violating the legislation is punishable by up to five years in jail.

“A British national was arrested and charged with illegal possession of war weapons last night at the airport,” airport policeman Somchart Maneerat told AFP Tuesday.

His German coworker was also detained, the officer said.

Media groups have repeatedly criticised the Thai law and say journalists should not be punished for carrying body armour and protective gear in and out of dangerous zones.

Late Monday Cheng posted a photo on Facebook of the airport detention cell where he was held overnight.

The plates and gas mask were “for use in Mosul where ISIS are well documented to be using gas,” he wrote.

“I was unaware either of those things were classified as ‘war weapons'”.

Attempts over the years to amend the legislation have fallen on deaf ears, despite Thailand’s own history of deadly street protests and a festering Muslim insurgency in the far south.

“Journalists who feel they need to carry this stuff need to inform or contact the concerned authorities prior to travelling,” junta spokesman Major General Werachon Sukhonhapatipak told AFP.

In August 2015 a Hong Kong photographer was charged with violating the law for carrying a bullet-proof vest and helmet while covering a deadly bombing in Bangkok. A Thai court later dropped the case.

During Thailand’s regular bouts of often violent street protests, both demonstrators and journalists have donned ballistic vests and helmets, largely without falling foul of police.

Two foreign reporters were killed by gunfire while covering the worst round of political unrest in 2010.