For example why not tell Seyni Kountché in Niger that he had to have elections?
There are two clues in the title: former colonial powers, and decolonization, the ending of colonial status. A presumption of independent statehood is (or at least was in theory) that other states don't dictate your internal political system to you when things go off-script, otherwise there's not much point to independence.
The commonly-accepted rules of international law are those enshrined in the 1945 UN Charter and subsequent international conventions and UN resolutions, and the associated rulings of the International Court of Justice. u/PhiloSpo has outlined some of the legal background, noting the key Article 2, section 4 of the UN Charter. General Assembly resolution 2131 (the Declaration on the Inadmissibility of Intervention in the Domestic Affairs of States) went further:
No state has the right to intervene, directly or indirectly, for any reason whatever, in the internal or external affairs of any other state.
Note that there's nothing in either provision limiting the right to political independence to countries with civilian or elected regimes: it's subject only to compliance with compliance with the fundamental requirements of the Charter, notably non-aggression against others. The principle doesn't override the UN's right to act (or authorise action by others) to keep the peace or respond to other extreme emergencies: innovations such as the 1948 genocide convention hinted at a possibility of internationally-agreed action, though the qualifying conditions and appropriate responses remained undefined.
But having a coup of cancelling elections doesn't override the principle of sovereignty. That shouldn't surprise us when we recall that the UN of 1945 or 1965 included countries with a remarkably diverse range of regimes, from western states with regular elections to one-party governments or military regimes with at best strictly limited voting.
It's worth recalling that Kountché's wasn't the most notable coup of April 1974. Only ten days afterward another toppled the 48-year Salazar-Caetano regime in Portugal, which despite holding nominal elections quashed all effective opposition to maintain itself in power. Neighbouring Spain had an even worse dictatorship under Franco, whose adoption of limited sham voting in 1967 came three decades after the last election. Spain wouldn't see a real election until 1977.
But the west did nothing about Franco or Salazar - or about the 1967-74 military regime in Greece (like Portugal a Nato member) - as indeed strict compliance with the Charter dictated (although enforcement of non-intervention during the Civil War would have made Franco's bloody seizure of power more difficult).
And the fragility of constitutional politics in Africa from the 1960s isn't altogether surprising when we recall that the first forays into elected government in most of the continent came only in the late 1940s or more commonly the 1950s. The former colonial powers had been content to rule for half a century or more without such formalities, weakening any claim to be democracy's champions. The then Belgian Congo got its general election five weeks before independence: the new government lasted ten weeks before being sacked by a pro-western president as the country descended into civil war.
And intervention usually just wasn't essential to western interests, indeed undemocratic regimes might be considered easier to work with than the alternative. The cosy "constructive engagement" relationship with apartheid-era South Africa (where power was limited to the white sixth of the population) reminds us that democracy and political inclusion weren't the overriding priorities of the day.
So in sum, western countries didn't generally intervene in African coups because in those days it was considered contrary to international law (though that of course didn't stop less overt involvement, often against elected governments), and because its moral case for doing so wasn't what you'd call watertight, and because geopolitical or economic interest tended to trump ethical policy.
As the moderators already stated, questions like this are notoriously troublesome to argue against. One can try shed light on some expected issues that would have arisen had the countries engaged in such actions, what were the deterrents for such courses of action, and what did the countries learn from such courses of action already taken in various independence wars. It would be highly problematic to engage in a conflict yet again, that not only did it brought foreign disapproval, but domestic turmoil as well. We also have to consider that in some cases, the west ( and here mostly USA ) was better of and actually silently supported various coups, but also, any overt military intervention on the heights of Cold War would brought reprisals and counter-action from the other sphere ( USSR ). If the precedent was set that an overt military intervention was possible given the disapproval of internal policies of a country, there would be a substantial difficulty in reversing the precedent. Then there is the UN. But I should develop these issues more thoroughly in following subsections:
Laws of war, jus ad bellumCharter of the United Nations, Article 2(4):
All members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.
The Article is considered today as a part customary international law, which is obligatory even for non-signed states if they have not objected to the said law prior to conflict. But even in this case, some laws are credited as jus cogens - peremptory norm, from them, all deviation is considered unlawful. Though there is no universal agreement, war of aggression is considered one of them.
Article 39 of the Charter:
The Security Council shall determine the existence of any threat to the peace, breach of the peace, or act of aggression and shall make recommendations, or decide what measures shall be taken in accordance with Articles 41 and 42, to maintain or restore international peace and security.
Given the composition, such unilateral response was unlikely, and certainly not for the reason stated in the question.
UN, Policy - foreign and domestic
Since the question is so unspecific, (1) the issue of the term "step in", Secondly (2) I will try to establish some general results from already executed courses of such actions ( ie interventions ) (3) and probable results if such an action was undertaken, (4) what was the usual course of action during the regime change.
(1) Henceforth I shall equate, and subsequently focus next points accordingly, "step in" as an overt military intervention that is the result of a preceding coup.
(2) Here the nature of indeterminacy and generality of the question makes compounding a constructive argument for it rather difficult, not only because the complexity of the period, but because direct military interventions outside of UN were rare. Since the condition is overt military action after a coup, the example will be Panama intervention. But this intervention, to be generalized, is again problematic. It was at the end of cold war and one of the major factors - bipolarity - was at its end. Also, the intervention had general support in Panama.
A CBS News poll in Panama in early January found that 92 percent of Panamanian adults approved of the sending of troops, and 76 percent wished the United States had sent them during the coup in October. The American people also approved of the invasion: 74 percent said it was justified, and only 7 percent thought the United States should not have taken such action. More significantly, the invasion measurably improved Bush's over all approval ratings, lifting him to 76 percent, a higher level at that point in his term than any president had achieved since John R Kennedy^(1).
But USA had a tangible interest here, beside the Panama canal, the protection of US citizens along the Panama canal, together with domestic unpopularity of Noriega.
Therefore, the nature of this course of action is hardly applicable to previous occasions that could have resulted during the cold war.
(3) Since we do not have a clear example that would fall into the category, one could make a tangible case for joint Israel-UK-France action in 1956 towards Egypt, why it failed, and what was the role of USA.Firstly;
There has been much speculation as to whether the CIA was behind the Egyptian coup, particularly in Egypt. Stories abound in Egypt about how CIA operatives met Abdel Nasser several months beforehand, knowing him only as “Maurice,” and how Ambassador Jefferson Caffery used to call the Free Officers who ran the coup “my boys.” Caffery’s posting to Cairo has also aroused suspicion, since his previous posting was as Ambassador to Paris, from which Cairo appeared to many to be something of a demotion. There undeniably were contacts before the coup between David Evans, the Embassy’s Air Force liaison, and Ali Sabri, the head of Egyptian Air Force intelligence and one of the Free Officers. Yet, declassified Embassy records consistently show a lack of definite foreknowledge that the coup was underway. Further, the Embassy’s political officer, William Lakeland, told this author that Muhammad Hassanein Heikal, an Egyptian journalist who was close to the coup plotters, suggested vaguely to him several days before the coup that “something might be happening.” Lakeland’s reporting cable to Washington suggesting a possibly imminent coup was toned down significantly by the Ambassador, who thought it unlikely. Lakeland thought it highly improbable that the CIA had any contact with the Free Officers before the coup; however, he thought it quite possible that the American Embassy had contacted the British Embassy at about the time the coup took place, asking that the British army not intervene and thus allow the coup to unfold^(2).
Again we are thwarted to make general statements due to the peculiarity of the situation, as the USA opposed the intervention ( Also USSR and UN ), and as the result of it, it did not succeed.
(4) The collection of these cases establish to a degree the difficulty of over action. That is why the prefered and often used course of action was covert and implicit, either as political or economical pressure, or both, or if the state was already in turmoil, the support of a fraction, usually on the basis of bipolarity.
Another point is that I would like to return to is precedence, and use the Congo crisis as the example. Direct Soviet arms transport ^(3,4) set a precedence for likewise activity of the USA.
Conclusion
I would assume that from the synthesis of arguments presented above the infeasibility of such actions is clearer. Though one would have to go into specifics and argue the cases state by state of intervening states and state by state of states being intervened with. But that would require a more-in-depth and specific question.
Hey there,
Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.
If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!