A Kenyan human rights lawyer was expelled from Tanzania on Sunday following her attempt to attend the trial of an opposition figure facing treason charges.

Martha Karua—a lawyer, former minister of justice, and former presidential candidate in Kenya—was initially detained before being deported from the airport in Dar Es Salaam, Tanzania’s largest city. While detained, Karua stated on X that the authorities did not provide her with a reason for her detention.

The Law Society of Kenya, of which Karua is a member, labelled the decision as an “illegal and arbitrary denial of entry,” criticizing what they called a refusal of authorities to provide any reasoning behind such actions.

According to the society, the decision violates the principle of the free movement of people enshrined in the Treaty for the Establishment of the East African Community (EAC). Article 104 stipulates that “partner states agree to adopt measures to achieve free movement of persons, labour and services.” Additionally, the society stated that the detention reflects the dire state of “constitutionalism, rule of law and democracy in Tanzania,” a country bound by the provisions of EAC.

Amnesty International of Kenya stated that denying Karua entry into Tanzania threatens the values enshrined in international human rights law and undermines the trust in electoral and judicial processes in the country, unsuccessfully demanding that Karua be granted access to observe the trial.

Amid the ongoing treason trial of Tundu Lissu, the leader of Tanzania’s main opposition party, Karua has heavily criticized “democratic backsliding” in the country and the whole East African community.