After Ex-Spy’s Poisoning, EU Action on Russia Is Far From a Sure Thing

What the EU does is a test of Theresa May’s stated desire for the U.K. to maintain a close security relationship with the EU post-Brexit

It isn’t yet completely clear who poisoned former Russian spy Sergei Skripal or why. But if the nerve-agent attack two weeks ago in the English city of Salisbury was launched by the Kremlin partly to expose weakness and division in Europe, then it could hardly have been better timed.

The European Union is engaged in increasingly acrimonious negotiations with the U.K. over Brexit; the Italian election two weeks ago resulted in more than half the seats in the new parliament being taken by parties with pro-Kremlin sympathies;...