Whether the incident in France happened or not, one of our flight attendants years ago had a fully loaded 747-400 with pasengers aboard impounded! The company payroll computer was over two weeks late with her pay check. She contacted the local Wayne County Sherriff (whether an attorney was used or not, I don't know) near Detroit Airport in Michigan and he went to the aircraft and put some sort of lock on the nosegear. Supposedly, this was legal. A company executive sent her the long-overdue paycheck very quickly.
But I have no sympathy for such actions, especially when one country does that to an aircraft from another country, unless it is found to be in an unairworthy condition. Did Britain recently impound a foreign B-707 due to airworthiness issues?