Sophia Tesfamariam, Ambassador and Permanent Representative of Eritrea to the UN, sent a letter to the UNSC. She explained Eritrea’s involvement in the Tigray region. However, the letter’s stratagem does more harm than good https://www.ethiopia-insight.com/2021/04/29/bluff-and-subterfuge-eritreas-letter-to-the-un/

However, the letter’s stratagem does more harm than good by implicating the Eritrean government in the aggression of a sovereign nation and war crimes. The tensions between TPLF and the federal government of Ethiopia is an internal Ethiopian matter.

Strictly speaking, the letter itself is an illegal interference into the affairs of Ethiopia.

Therefore, through its letter, Eritrea confirmed that it had violated Ethiopia’s sovereignty when it deployed its army and security personnel in Tigray.

One may argue that Eritrea is doing all these at the will of the Ethiopian regime and, therefore, not breaching Ethiopia’s sovereignty. But then again, we have not yet heard any formal (or informal) invitation of Eritrea by the Ethiopian government led by Prime Minister Abiy

Moreover, Eritrea isn't entitled under international law to intervene in a civil war situation even if it was invited. The concept of sovereignty extends beyond a government in office. It embraces the people, the territory, and the territorial and political integrity of a country

Nor do Abiy Ahmed’s prime ministerial powers give him the authority to bargain Ethiopia’s sovereignty.

First, the Eritrean regime might argue that rockets fired by the Tigrayan forces attacked it first and that it acted in self-defense. But, the rocket attacks on Asmara happened more than a week after Eritrea launched a full-scale military operation in Tigray.