Summary: "By the Stalinist era of the 1930s, it was clear that the party and government made the rules and that the trade unions were not permitted to challenge them in any substantial way," Wikipedia says
"In the United Kingdom, the Foreign Enlistment Act 1819 and the Foreign Enlistment Act 1870 make it unlawful for British subjects to join the armed forces of any state warring with another state at peace with Britain."
Summary: "By the Stalinist era of the 1930s, it was clear that the party and government made the rules and that the trade unions were not permitted to challenge them in any substantial way," Wikipedia says