This is a tricky one.
The traditional answer is “no”. States are sovereign. How State A conducts its internal affairs is no concern of State B, and vice versa. States have a right to govern themselves and conduct their own affairs. They do not have to account to one another. They do not have rights to interfere in the affairs of other states. That’s what sovereignty means.
It’s only in the international sphere, where States interact with one another, that they can take a legitimate interest in one another’s affairs.
So, for example, State A kills it’s own citizens. That is no concern of other states. But State A sends its forces into State B and kills the citizens of State B. This is an infringement of the sovereignty of State B, and so is a matter of concern not only to State B but to all other states.
Sovereignty sounds like a noble concept, but it’s more of a pragmatic one. It limits international conflict. If the government of State A is entitled to make judgments about how the internal affairs of States B, C, D, E and so forth should be conducted, and is entitled to enforce those judgments through arms, the governments of States B, C, D and so forth all have similar rights. Given that each government will generally act in the interests of its own state, if we accept this principle we have more or less created a mechanism designed to justify State A (or any state) in going to war with State B (or any other state) in order to force State B to conduct its internal affairs in a way which will advance the interests of State A. We can see how this would rapidly descend into bloody chaos. Hence the principle of sovereignty, in the interests of mutual self-preservation.
But the principle has been coming under strain, particularly since the Second World War. Are we really happy with an international regime which says, basically, that Hitler can round up and murder every Jew, Gypsy, homosexual and communist in Germany, and no other state is entitled to intervene? No, is the answer, we’re not.
But states don’t want to abandon entirely the principle of sovereignty. So they attempt to develop some limitations on that principle.
The first is the development of humanitarian law. While in general the affairs of State A are a matter for the government of State A and no-one else, the argument goes, there are certain minimum principles of human rights which the government must respect and, if it fails to do so, this becomes a legitimate concern to other states. You can justify this by saying that gross breaches of human rights within one state will affect other states by creating a refugee problem, or a civil war with likely spillover, or simply by saying that fundamental human rights have an intrinsic value which all states have an interest in protecting, and a duty to protect.
But states themselves are a bit wary of this, because any limitation on the principle of sovereignty \affects all states. The US, for example, has a proud record in the field of the legal protection of human rights, and yet it deploys the death penalty against its own citizens in a way which would certainly be regarded as a breach of human rights principles by most European countries. The US insists that this is nobody’s business but its own, and it is reluctant to adopt any stance with respect to other countries which might weaken that position. And if the US feels at all vulnerable about external scrutiny of its domestic human rights standards, you can take it that almost every other state has at least as much reason to feel vulnerable.
So states are wary of this. At the very least, it requires the international development of agreed fundamental principles of human rights. The US would never accept that its internal affairs should be regulated by (say) UK perceptions of fundamental human rights, and it will not expect other states to accept that their affairs should be regulated by US perceptions. Hence the development of international human rights standards, to which states adhere, and against which they can be judged.
But even if we have an agreed standard, we still have the problem of deciding whether a particular state has infringed it in any given case. Can this be decided unilaterally by another state? Again, most states would answer “no”, because they don’t want to be on the receiving end of such a decision by a powerful neighbour.
And, I think, this is correct. The primary duty and interest of the government of State A is to protect and advance the interests of State A. To ask the government of State A to make, and enforce, a decision about whether the human rights of the people of State B are being adequately respected, without regard to the interests of State A, is wholly unrealistic. We would rapidly human rights becoming a political fig-leaf for the otherwise naked armed assertioni of the self-interest of other states. (Many, indeed, are tempted to see the Iraqi intervention in precisely these terms. It isn’t, for reasons I discuss below. But if these principles were accepted we would certainly see cases where this did happen.)
Hence the only feasible mechanism is one which involves a collective or consensus decision on the part of the international community that human rights are being abused to an extent which requires armed intervention. I appreciate that such a decision would still be a political decision and (at least as long as international bodies are structured as the UN is) could not be taken if it appeared to be contrary to the interests of the major powers. But at least such a decision could be taken in some cases, and could command international support, and it would be very difficult (though not impossible) for such a decision to be taken as a cover for the self-interest of any state, however powerful.
Of course, we’re not there yet. Most states are signed up to the notion that the protection of individual human rights is a legitimate concern of international law, but not to the notion that this can be done by armed intervention. So the question of who would take a decision about armed intervention is not even on the radar as far as they are concerned.
Not wishing to be contentious, but Iraq is an interesting example. The grossest breaches of human rights were ignored in the 1980s by the major powers, partly because Iraq was a handy distraction for, and limitation upon, the fundamentalist Iranian regime, but partly because they were internal to Iraq, and there was neither precedent nor political appetite to invade Iraq to enforce human rights standards on behalf of the Iraqi people. Iraq pretty well got away with everything until it invaded Kuwait. By transgressing the sovereignty of another state (which was not itself something of a pariah state) in this way it had crossed an important line. The major powers and the international community were willing to act – and they did, rapidly and effectively.
Fast forward to 2003. Since the Kuwait debacle, Iraq has not invaded or attacked another country, because it knows what the international response would be. The US finds it extraordinarily difficult to muster an international consensus for armed intervention in Iraq, precisely because this factor of the breach of another state’s sovereignty is lacking. Nevertheless, as we know, the US does intervene. As the various justifications for doing so (Iraq was involved in anti-US terrorism, Iraq had a large arsenal of ready-to-use WMDs) evaporate in an embarrassing fashion, the US has resisted the temptation to use Sadaam’s undeniable human rights breaches as a justification for intervention. They have suggested that Sadaam’s human rights record provides a reason why we should welcome his downfall, but they have never suggested either that they were motivated to invade to protect the human rights of the Iraqi people, or that such a motivation would have provided a legitimate reason to invade. The official position of the US government, I am pretty sure, is still that it would not.