Vladimir Putin has invaded Ukraine, propped up Syria’s Assad regime, meddled in the 2016 U.S. presidential elections, and this month someone in his government approved a chemical-weapons attack on British soil. The Western response so far is the equivalent of a foot stomp and public whining.

Start in Britain, where Prime Minister Theresa May on Wednesday outlined her response to evidence that Russia-backed agents used the Soviet-era Novichok nerve agent to try to assassinate former spy Sergei Skripal and his daughter Yulia...