THE exercise of violence is a subject where it is very easy for people to become either sanctimonious or cynical, and almost impossible for governments to avoid well-founded criticism. The fact that Marxists – themselves, of course, supporters of an explicitly violent doctrine – bandy about phrases like “the violence inherent in the system” doesn’t mean that there isn’t any. Most political theories grapple with how violence is used to obtain or preserve power, and how governing powers attempt to reserve for themselves a supposedly exclusive “right” to use it.

Even those who believe that liberal Western democracies are fundamentally benign and beneficial should concede that order and the rights of their citizens is preserved by a state monopoly on the use of physical, violent force; both internationally, with standing armed forces and war or the threat of it, and domestically, through the police, courts and prison services.

The development of centuries of theological, philosophical and political theories tackling this issue has led to widely accepted conventions. They include things like treaties on the treatment of prisoners of war, prohibition of particular kinds of weapons and measures designed to minimise harm to civilians in war zones.

The 20th century, which saw warfare, genocide and the oppression of domestic opposition practised on a hitherto unknown scale, may not have provided very compelling reasons to believe that we are improving on the past. But since at least the end of the Second World War, the existence of America as a military superpower, and the democratic nature of most developed economies, has led to some norms emerging. The “international community”, insofar as such a thing exists, particularly condemns the use of murder against opponents of governing regimes. Unless, under President Trump, that is no longer the case. At least three of the countries that most interest Mr Trump – whose knowledge and understanding of foreign affairs is not his foremost feature – have committed recent brazen assassinations of opponents of their regimes. And done so on foreign soil, while those people were nominally or expressly under the protection of other countries.

In February last year, Kim Jong-nam, the half-brother of the North Korean dictator Kim Jong-un, was murdered at Kuala Lumpur airport with a nerve agent. That the Russian secret service has killed, or attempted to, numerous opponents of Vladimir Putin’s regime is no longer doubted by anyone other than a few tinfoil-hatted conspiracy theorists. Most recently, in what appears to be an equally clear-cut case, Jamal Khashoggi, a journalist and critic of the Saudi regime based in the US, was apprehended, tortured, murdered and dismembered in the Saudi consulate in Turkey.

There was a time when extra-judicial murders such as these would have been greeted with clear condemnation, and almost certainly with political and economic, if not military, reprisals. The US Treasury Secretary Steven Mnuchin may have now pulled out of an investment conference in Saudi Arabia,but Mr Trump’s initial response seems to have been to ring up the Saudis and attempt to provide them with a plausible story. Naturally, no one, not even Mr Trump, could have taken the malleability of the real world as far as imagining that the Saudi authorities were not behind the killing.

It’s hard enough to imagine anyone credulous or cynical enough to advance the view that Mohammed bin Salman, the prince who now runs the country, didn’t know anything about the arrival of 15 of his country’s black ops at the Turkish consulate. Especially since MBS (as he’s known) has a stellar track record of oppression, even by the standards of Saudi brutality. Yet this is the line that Mr Trump is not only indicating might fly, but actually appears to be suggesting to the Saudi leadership. Meanwhile, Kim Jong-un continues to receive Mr Trump’s approval. (The small detail of his running perhaps the world’s most repressive regime isn’t much of a consideration.)

It’s almost irrelevant whether Mr Putin, as everyone assumes, “has got something” on Mr Trump in terms of kompromat. It’s clear that, had it not been for the almost cartoonish ineptitude of the Russian intelligence agents who attempted to murder the Skripals, and those arrested in the Netherlands trying to cover it up, he would still be cheerfully wiping out anyone with a disobliging word to say about him without a murmur from the White House. This is the point at which the cynics, the scriptwriters of Hollywood political thrillers and those whose Leftist credentials make it an article of faith that Western countries should be in the wrong (that’s you, Jeremy Corbyn) step forward and argue that, since no country or regime is Caesar’s wife, it’s hypocritical to point the finger at Brutus or Casca.

Or Castro. “Did the US not make numerous unsuccessful attempts to assassinate Fidel?” they ask piously, ignoring the late Cuban leader’s highly successful attempts to murder his own opposition. But therein lies the distinction, though we may very well find it morally unsatisfactory. The US government has sometimes killed, or tried to kill, those whom it believed threatened its own security. In the cases of Castro and other inconvenient leaders, such as Rafael Trujillo, Salvador Allende and Patrice Lumumba, there is comprehensive evidence for it.

But, at least since Gerald Ford’s edict in the mid-1970s, such actions have been specifically prohibited by US law itself. It’s worth noting that the killing of terrorists by drones and missiles under Presidents Bush and Obama, and the death of Osama bin Laden, were not “assassinations”, but “targeted attacks” part of nominally military operations.

You may think this is a distinction without a difference, but there is at least one: it indicated where a democratic, non-authoritarian government thought the line was, and acknowledged that, when stepping over it, it was in the wrong. The worrying thing is that Mr Trump is not merely ignoring that stance, nor even just giving them excuses for it, but seems to have an active admiration of it.