British Prime Minister Theresa May's immediate response to the poisoning of Russian double agent Sergei Skripal in Salisbury won't impress anyone in the Kremlin.

May, however, has indicated a promising line of attack on President Vladimir Putin's regime: an international effort to punish Russia for maintaining an undeclared stockpile of chemical weapons.

May announced the expulsion of 23 Russian diplomats "identified as undeclared intelligence officers," the biggest one since 1971, when 90 Russians were forced to leave.

But the Kremlin has been prepared for this largely symbolic response, and it will not be hard to announce a symmetrical one before too long. All that will entail is a potential disruption to travel between Russia and the UK, like the one that followed tit-for-tat expulsions with the US last year.


No one in Moscow will shed a tear about May's other announcement: a break-off of high-level relations between the two countries. As Russian opposition leader Alexei Navalny tweeted sarcastically: "Members of the British royal family won't come to the opening of the soccer World Cup. Putin weeps from grief and ceases to kill people."

Navalny later deleted the tweet, as well as another one, saying that while 23 Russian diplomats will be expelled, 23 Russian oligarchs and officials "will continue enjoying London."

Perhaps he decided he was being too harsh on May. Devising a response to the Skripal poisoning was no easy task, after all.

A harsher punishment than one imposed on Russia for invading Crimea would hardly be justified, but responding as meekly as the UK did to the murder of another Russian on its soil, Alexander Litvinenko, would mean political trouble.

In that sense, the diplomat expulsion sent the right signal: Only four Russians were expelled following the Litvinenko case.

May couldn't very well announce the most effective yet symmetrical deterrent to Russian violence: ordering a similar operation against them on their turf. She had to confine herself to veiled threats.

"Of course, there are other measures we stand ready to deploy at any time, should we face further Russian provocation," she said.

This can include anything from cyberattacks to intelligence operations, but the Kremlin is expecting them, anyway: Russian leaders have been paranoid about covert Western interference for years. To them, it's all par for the course, Skripal or no Skripal.

Despite making threatening noises about acting against shadowy Russian wealth in the UK and hostile Russians in general, there appears to be no plan for a massive crackdown on the Russian money coursing through London's veins.

"To those who seek to do us harm, my message is simple: You are not welcome here," May said. But that's about as effective as signs I saw some years ago in Stratford-upon-Avon telling people not to feed the Canada geese because they were not welcome there (unlike the indigenous swans). The geese couldn't care less.

Nor did May discuss any economic sanctions against Russia, such as restrictions on Russian energy imports (the UK has been buying a lot of Russian liquefied natural gas lately) or an attempt to cut it off from the SWIFT system that facilitates money transfers. Any such measures could hurt the UK itself or run into resistance on the part of other European nations, which have been reluctant to sustain further economic losses from punishing Putin.

It would, however, be wrong to dismiss May's response as routine and ineffective.

In a statement, the North Atlantic Treaty Organisation discussed the attack on Skripal and his daughter Julia as "the first offensive use of a nerve agent on Alliance territory since Nato's foundation."

That may not be enough to trigger Nato's Article 5 mutual defence, as in the aftermath of the September 11 attacks. But it's the beginning of what could be the most powerful attack on Russia's international standing since Putin grabbed Crimea.

Putin has already been accused by Western nations, particularly the US, of not keeping his promise to help destroy all the chemical weapons stockpiled by President Bashar al-Assad's regime.

Assad has been blamed for a number of chemical attacks in recent years, and Russia has been named in various forums as an accomplice. Now Russia is facing demands to disclose weapons it has apparently stockpiled itself - just as Vil Mirzayanov, the whistleblower who disclosed the existence of the Novichok binary weapon programme, warned in the early 1990s.

Mirzayanov wrote in his book, State Secrets, that the Novichok family of nerve agents was developed with a view to non-disclosure under chemical weapons treaties: It was based on a common pesticide that turned into deadly poison only as it reacted with another compound. Now that a Novichok agent has been used to poison Skripal, Russia will face considerably more pressure to reveal the stockpile.

Official Moscow can try to insist that its last chemical weapons were destroyed last year. It can also try a tactic it developed in Syria, claiming the use of the chemical was a false flag operation (perhaps blaming Ukraine, as some commentators on Russian state TV have already said).

Both these lines of defence, however, are likely to grow less credible as the British investigation progresses, especially if it's established with reasonable certainty that the nerve agent could only have been deployed by someone linked to the Russian government. No country will condone the use of chemical weapons, whatever the economic consequences of a harsh sanction regime.

Putin's Kremlin will probably ignore the early warnings and keep up its brinkmanship. It may find this a mistake soon, as countries are faced with evidence of a Russian chemical weapon deployment on foreign soil.

- Bershidsky is a Bloomberg View columnist. He was the founding editor of the Russian business daily Vedomosti and founded the opinion website