I just learned that 50% of Russian government tax receipts come from oil & gas revenue. With one simple decision - banning oil & gas imports - we could devesta

I just learned that 50% of Russian government tax receipts come from oil & gas revenue. With one simple decision - banning oil & gas imports - we could devestate Putin’s ability to wage war and it would impose less direct hardship on everyday Russians? To protect civilians from higher energy costs in Ukraine and EU western governments could temporarily provide direct subsidies. This seems like an idea worth trying. What am I missing?