Shocking pictures from the Ukrainian town of Bucha and accusations of Russian war crimes are building pressure for more sanctions against Moscow. A key potential target: Russian oil and natural gas, and the $850 million that European importers pay for those supplies every day. But it’s not so easy, given Europe’s dependence on Russian energy. Western sanctions so far have targeted Russian banks and companies but spared oil and gas payments because a boycott would cost Europe economic growth and jobs. Some economists propose an alternative: A stiff tariff on Russian energy imports to sap the Kremlin’s revenue.