The Legion has reported 25 desertions by Ukrainian-born soldiers, with around a dozen of them believed to be planning to help the fight against the Russian army.
The Legion has “cut them loose”, commander Alain Lardet told AFP. “They are fighting for a cause that it is not my role to judge.”
Nine in the group that were stopped were on leave but not authorised to travel abroad when they were stopped Tuesday in Paris. The others were absent without leave or considered missing, added Lardet.
They were arrested on a coach headed for Poland neighbouring Ukraine, which has been battling a Russian invasion for the past week.
The Foreign Legion, an elite corps comprising around 9,500 soldiers, is the only French army unit in which foreign nationals can enlist.
They qualify for French nationality after several years of service, or sooner if they distinguish themselves in battle.
It was not immediately clear whether the 14 were planning to join the fighting in Ukraine, or simply help their families who had fled Ukraine, the military command said. No weapons or other unauthorised equipment was found on them.
But some of the civilian passengers on the bus were carrying gear that led the authorities to believe that they were planning to join the fighting.
The Foreign Legion counts 710 soldiers of Ukrainian origin of whom 210 have been naturalised, and 450 Russian-born troops.
While there has been “no tension between the communities” since Russia invaded its neighbour, Ukrainians in the Foreign Legion have been “very worried for their families”, Lardet said.
They can apply for an exceptional two-week leave to travel to one of Ukraine’s neighbouring countries to assist their families fleeing the war, but are not authorised to cross into Ukraine itself, he said.
On Tuesday, 25 such permits were granted, with several more expected Wednesday, but none of the Ukrainians arrested on Tuesday were in possession of such a document.
The nine who had regular leave for France only are unlikely to be punished because they had not been told properly that there was now a legal way to join their families, the commander said.
But the five others will be ordered into military detention for an unspecified number of days, having committed “a serious violation of the Legion members’ code of honour”, he said.