By now, it really should not come as much of a surprise that yet another Russian has been attacked in Britain. Opponents of Russian President Vladimir Putin have been showing up dead in and around London for more than a decade. In some cases, the trail clearly leads back to Moscow with the use of such gruesome chemical agents as polonium (Alexander Litvinenko in 2006) or, in the most recent incident, a nerve agent (Sergei Skripal and his daughter, who both survived the poisoning but remain in serious condition). In other cases, the evidence is subtler (Boris Berezovsky, found dead under suspicious circumstances in 2013).

While Britain is not the only place where those who have run afoul of Putin have died, a troublingly high number of such deaths have happened there. We can quickly dispense with the blathering of Russian officials about the latest case as just that: blathering. Putin’s public policy plan for this type of thing can be summed up as, “Lie bigger, lie harder; sooner or later, the West will forget.”

It’s a plan that often works.

Why the Russian Government decided to make the attempt on Skripal is not a difficult question. News reports have indicated that Skripal is a former Russian intelligence officer who was sent to a Russian prison in 2006 for selling state secrets to British intelligence. He was freed in 2010 in exchange for Russian intelligence officers arrested in the United States. Putin apparently decided to send a strong message to current and future members of the Russian intelligence services: If you co-operate with the West, we will find you and kill you even if you end up living outside Russia.

The use of poisons in attempted assassinations (most likely performed by the Russian external intelligence service, the SVR, or possibly the military service, the GRU) has an added psychological element. In effect, Putin is saying: Not only will we find and kill you, we will do it in particularly gruesome fashion. Your family may also be targeted. If you’d like a glimpse of the agony that Putin is trying to impart to potential spies, take a look at the online photographs from the last days in the life of Litvinenko.

That so many of these attacks have occurred on British soil puts Prime Minister Theresa May and her government in a difficult position. They are now well past the standard diplomatic response: Call in the Russian ambassador, express grave concerns and perhaps expel a number of Russian personnel from the embassy in London (which would almost certainly prompt a reciprocal expulsion of British diplomats from Moscow). London could also consider unilateral financial sanctions, but the rub there is that, given the amount of Russian business and investment in the United Kingdom, this could significantly hurt British interests as well.

Putin has shown himself to be expert at understanding the difficulties that open Western societies have when it comes to punishing Russia for illegal acts. Whether it is annexing part of another country, as he did with Crimea, or having the Russian intelligence services attempt assassinations on foreign soil, Putin has calculated that Russia can weather any storm the West can come up with in response. Yes, Russia paid something of a price in sanctions after the annexation of Crimea, but not enough to really worry Putin and his oligarchs, who by and large simply pass the suffering along to the Russian people. The Kremlin knows that eventually the sanctions will be lifted. Putin also knows that the West is not eager for direct military confrontation. That leaves him with plenty of room to manoeuvre.

And yet a significant response is required. This was a not only a Russian attack on Skripal but, as May put it, “an illegal use of force” that endangered scores, if not hundreds, of British citizens in their own country. And it is clear that strongly worded messages are not the language Putin understands best: Actions, in these situations, speak louder than words. So, what are the options?

If Britain acts unilaterally, its best response probably is economic. Finding a way to freeze or otherwise immobilise Russian capital in the British financial system would be effective, especially if a key group of Russian oligarchs were targeted. Another measure could be to cancel British visas held by a list of Russian oligarchs — which might not hurt the Russian economy that much but would send a strong message by upending the lives of a group of people Putin does pay attention to. Hopefully there are creative statesmen and economists in London who can figure out methods to target the only real power group in Moscow that could threaten Putin: his oligarchs.

But the West should also rally behind Britain — quickly, publicly and unequivocally. Putin has been clever by using his intelligence services in this attack, thus robbing Nato and the United Nations of a specific casus belli against Russia. Yes, using a military-grade nerve agent that only Russia could have produced does have a military element to it, but this was not a full-on military attack against Britain. It has the deniability all Russian active measures have. Still, it’s not out of the question for Nato to invoke Article 5, declaring that this attack didn’t threaten just Britain but all Nato countries.

Again, though, Putin has probably already gamed this out. It would be difficult to get all Nato countries on board with this plan, and, after all was said and done, what would it mean? Would Nato launch a military attack? That is unlikely.

There are other options the United States and the international community should consider. They would be highly controversial, but at some point, our global structures must be used to punish horrific, illegal behaviours by those who want to participate in the international system. The first would be to consider banning official Russian use of the Swift international banking system. This would have an immediate impact on Putin, his oligarchs and the Russian economy in a more significant way than just economic sanctions. Russian officials have said in the past that such a measure would be tantamount to war, an indicator of how seriously they would take the threat.

Another option would be to at least raise the issue of suspending or removing Russia from the UN Security Council, under the premise that a country that undertakes extraterritorial assassinations or illegally annexes parts of neighbouring countries has forfeited its right to be on the council.

All these approaches have one thing in common: They are fraught with difficulties and would test the resolve of Western democracies, which are currently divided along sociopolitical fissures the Russians have worked hard to exacerbate. (President Trump, meanwhile, said on Tuesday morning that “as soon as we get the facts straight, if we agree with [the British assessment], we will condemn Russia or whoever it may be.”)

But if the West cannot muster a serious response to the use of chemical weapons on British soil to target someone Russian officials apparently viewed as a traitor for his work with British intelligence, what else will Putin try? If not now, under what circumstances would the West engage in serious measures designed to push back at Putin? What exactly would it take beyond international assassinations and illegal annexations to trigger a serious response to which the Kremlin would pay attention? Putin has already engaged in actions that should outrage the international community. What more will that same community let him get away with?

• Steven L. Hall retired from the CIA in 2015 after 30 years of running and managing Russian operations