Ethiopia took the lead in creating Africa's continental organisation, the African Union (AU), but Ethiopia analyst Alex de Waal argues that its actions are now jeopardising the body's founding principles.
Shortly before three former African heads of state arrived in Ethiopia's capital, Addis Ababa, to seek a peaceful resolution to the conflict in the northern Tigray region, Prime Minister Abiy Ahmed ordered what he called the "final phase of our rule of law operations".
This was a remarkable rebuff.
Former Presidents Ellen Johnson Sirleaf of Liberia, Joachim Chissano of Mozambique and Kgalema Motlanthe of South Africa met Mr Abiy on Friday, but were told that the Ethiopian government would continue its military operations.
Mr Abiy also said that they could not meet any representatives of the group Ethiopia is fighting in Tigray, the Tigray People's Liberation Front (TPLF), which the prime minister has dismissed as a "criminal clique".
Citing the Charter of the United Nations in a statement earlier in the week, the prime minister insisted that the federal government was engaged in a domestic law-enforcement operation and the principle of non-interference in the internal affairs of a sovereign nation applied.
But Nigerian legal expert Chidi Odinkalu argues that Ethiopia is using the charter to escalate a war, the opposite of its pacific intent, saying that the "audacity of this position is disconcerting".
He points out that the conflict is already internationalised, because Eritrea is entangled and refugees are crossing into Sudan.
Also, the United Nations has adopted principles to prevent states abusing the doctrine of non-interference to give themselves impunity to commit atrocities.
Since 1981, conflict resolution has been a duty and a right. Since 2005, states have had the responsibility to protect civilians in conflict.
Fears of war crimes
In rebuffing the African mediators, Mr Abiy is not just turning down a peace initiative. He is challenging the foundational principles of the African Union itself.
Article 4(g) of the AU's Constitutive Act - to which Ethiopia acceded in 2002 - does specify "non-interference by any member state in the internal affairs of another".
But this is immediately followed by Article 4(h), which gives the AU the right "to intervene in a member state… in respect of grave circumstances, namely: war crimes, genocide and crimes against humanity".
This so-called "duty of non-indifference" was adopted in the wake of the 1994 genocide in Rwanda.
It was first formulated by an International Panel of Eminent Personalities, strongly supported by Ethiopia, which was brought together to recommend how Africa should prevent such atrocities in the future. "Non-indifference" is Africa's version of the UN's "responsibility to protect".
The Ethiopian government has itself accused the TPLF of carrying out atrocities, and observers fear that when the news blackout is lifted, evidence of war crimes by both sides will come to light.
There are unconfirmed reports that Eritrean troops have crossed the border and rounded up Eritrean refugees in United Nations camps in Tigray, which would be a violation of the United Nations convention on refugees.
Ethiopia's diplomatic triumph
The Organisation of African Unity (OAU) was founded in 1963, with its headquarters in Addis Ababa, with the aim of consolidating the newly won independence of African states.
Locating the OAU in Ethiopia was a diplomatic triumph for Emperor Haile Selassie, who had long championed international law.
Famously, his 1936 speech at the League of Nations predicted that if Italy's invasion of Ethiopia were to go unpunished, the world would be bathed in blood.
The OAU was a common front for Africa's liberation from colonial and racist rule.
But it also served as a club of autocrats, who held to their common interest of staying in power no matter what. Tanzania's founding President, Julius Nyerere, lamented that it had become "a trade union of heads of state".
By the 1990s it was clear that the OAU needed to be refashioned to be able to respond to Africa's wars, coups and atrocities, and in 2002 the AU was created with a far more ambitious agenda of promoting peace and democracy.
Since then it has developed a set of mechanisms that include suspending countries where there is an unconstitutional change in government, and offering help to mediate conflicts, along with an obligation for conflict-afflicted countries to welcome good-faith peacemaking efforts.
How the African Union has helped
Mr Abiy himself intervened in the Sudanese crisis last year when he sought a peaceful resolution to the confrontation between the pro-democracy movement and the military, which had unseated President Omar al-Bashir.
The formula for Sudan's transition to democracy was drawn up on the AU's template.
But the AU is not a strong institution. It has a low budget and cannot impose its will.
More powerful states and organisations can overrule it - as Nato did when the AU sought a negotiated settlement to the Libya conflict in 2011, but the United States, European and Arab countries pursued regime change.
The AU's real value lies in its soft power: it articulates the norms of peace and cooperation and persuades African leaders to go along, knowing that they rise together and sink together.
Over time, it has proven its value: Africa has become more democratic and peaceable.
A generation ago, African diplomatic efforts to avoid conflicts or resolve them were rare. Today, they are standard practice.
Find out more about the Tigray crisis:
In a statement announcing the three envoys' mission, South African President Cyril Ramaphosa, who is the current AU chairperson, reaffirmed the organisation's position that the conflict "should be brought to an end through dialogue".
But it was couched in standard diplomatic courtesies and lacked bite.
In comparable situations - such as Libya or Sudan - the AU chair has convened a special heads of state meeting of the AU's Peace and Security Council. Mr Ramaphosa has not done that.
South Africa - which is currently one of three African nations on the UN Security Council - postponed a discussion on Ethiopia at the UN on Monday, citing the need to hear the envoys' report first.
Because it hosts its headquarters, Ethiopia has an outsized influence on the day-to-day affairs of the AU.
Other African countries have long suspected that it has a double standard, giving Ethiopia leeway that it does not accord to other countries. That did not matter so much when Ethiopia was active in supporting mediation efforts and peacekeeping operations, especially in Somalia, South Sudan and Sudan.
Now, many are asking if it has brazenly crossed a red line.
'The AU is for others, not Ethiopia'
The Ethiopian government has purged Tigrayan officers from AU and UN peacekeeping missions, according to a report in Foreign Policy magazine quoting a UN document. It also demanded that the AU Commission dismiss its head of security, who was a Tigrayan and whose loyalties were questioned because of the conflict.
And now Mr Abiy has effectively rejected Africa's highest-level mediators, politely recording only that they "imparted their wisdom, insights and readiness to support in any way they are needed".
After Ethiopian federal troops occupied the Tigrayan capital Mekelle on Saturday, Mr Abiy declared his operation complete - implying that he doesn't need peacemakers. But the African mediators - all from countries that have long experience of armed conflicts - are not likely to be so confident.
The AU headquarters was built on the site of Ethiopia's notorious central prison, known as Alem Bekagn - meaning "farewell to the world" in Amharic.
Thousands of political prisoners were imprisoned there, many tortured and executed, during the military dictatorship of the 1970s and 1980s. That symbolism is not lost on African civil society activists, who wonder if they are becoming prisoners of their Ethiopian hosts.
A senior AU diplomat remarked on Friday: "Abiy thinks that the AU is for others, not for Ethiopia."
Mr Abiy's rejection of mediation harkens back to an earlier era in which African civil wars were ended by force of arms, not peace agreements - leaving grievances to fester.
It threatens to make a mockery of the African Union's hard-won norms and principles of peacemaking.
Alex de Waal is the executive director of the World Peace Foundation at the Fletcher School of Global Affairs at Tufts University in the US. He worked for the AU on Sudan in different capacities from 2005 to 2012.