Self-Determination

Under international law, minority groups that qualify as “peoples” have the right to self-determination: the ability to freely determine their political fate and form a representative government.

Although no international treaty defines the term “people” for the purposes of self-determination, it is generally accepted that this classification entails a subjective element, such as a common belief by members of the group that they share the same characteristics and beliefs and thus form a common unit, as well as an objective element, such as common racial background, culture, ethnicity, religion, language, and history. Michael P. Scharf, Earned Sovereignty: Judicial Underpinnings, 31 DENV. J. INT’L L. & POL’Y 373, 373–79 (2003)[4]

A 'peoples' who are entitled to the right of self-determination tend to have a distinct history, ethnic identity, cultural homogeneity, linguistic unity, religious affinity, territorial connection and common economic life: …”
International Meeting of Experts on Further Study of the Concept of the Rights of Peoples: Report and Recommendations', UNESCO (1990), p. 38.

The theory of self-determination, as justifying the secession of a people from its existing mother state as a matter of last resort only, in situations where the people is oppressed or where the mother state’s government does not legitimately represent the people’s interests, has remained constant throughout the 20th century development of international law. Two United Nations’ declarations, in addition to the United Nations Charter itself, have addressed the issue of self-determination—the 1960 Declaration on the Granting of Independence to Colonial Countries and the 1970 Friendly Relations Declaration.
Declaration on the Granting of Independence to Colonial Countries and Peoples, G.A. Res. 1514 (Dec. 14, 1960); Declaration on Principles of International Law Concerning Friendly Relations and Co-operation Among States in Accordance with the Charter of the United Nations, G.A. Res. 2625 (Oct. 24, 1970).

“ … international law is neutral on secession—it does not support a right to secession nor does it prohibit secession. Instead, the secessionist dispute is left to the realm of domestic law and to political negotiations between the mother state and the secessionist entity.”[13]
[12]Marko Milanovic, A Footnote on Secession, EJIL: Talk! (Oct. 26, 2017)

Is Secession The Same As Overthrowing The Government?

No, secession is not a Coup D’état or the violent overthrow of the ruling government.  It is a lawful systematic process whereby a geographic portion of a country split off and forms a new country.

Is Supporting Secession An Act Of Treason Or Is It Constitutional?

Secession is a perfectly legal process found in the South African constitution:

Section 235 – South African Constitution

The right to self-determination is guaranteed in this section.  It reads as follows:

“The right of the South African people as a whole to self-determination, as manifested in this Constitution, does not preclude, within the framework of this right, recognition of the notion of the right of self-determination of any community sharing a common cultural and language heritage, within a territorial entity in the Republic or in any other way, determined by national legislation.”

Section 233 – South African Constitution

Moreover Section 233 of the constitution specifies that the constitution should be interpreted according to International Law:
“When interpreting any legislation, every court must prefer any reasonable interpretation of the legislation that is consistent with international law over any alternative interpretation that is inconsistent with international law.”

Secession is a perfectly legal process found in International Law:

Secession’s legality is defined as a ‘right of all peoples…’ under international law:

The African Union (AU) laws make provision for secession in its Article 20:

1. 'All peoples shall have the right to existence. They shall have the unquestionable and inalienable right to self-determination (secession). They shall freely determine their political status and shall pursue their economic and social development according to the policy they have freely chosen.'
2. 'Colonized or oppressed peoples shall have the right to free themselves from the bonds of domination by resorting to any means recognized by the international community.'

International Law
In international law, the right to self-determination (secession) is confirmed in article 1 of the International Covenant on Civil and Political Rights:

“1. All peoples have the right of self-determination (secession). By virtue of that right they freely determine their political status and freely pursue their economic, social and cultural development.

2. All peoples may, for their own ends, freely dispose of their natural wealth and without prejudice to any obligations arising out of international economic co-operation, based upon the principle of mutual benefit, and international law. In no case may a people be deprived of its own means of subsistence.

3. The States Parties to the present Covenant, including those having responsibility for the administration of Non-Self-Governing and Trust Territories, shall promote the realization of the right of self-determination (secession), and shall respect that right, in conformity with the provisions of the Charter of the United Nations.”

South Africa signed this international Covenant on 3 October 1994 which was then ratified on 10 December 1998.  The South African government is therefore legally bound by the Covenant's provisions which reads as follows:

“ … the formulation of common Article 1(1) within the two International Covenants on human rights left no doubt that the wording in the Declaration on the Granting of Independence to Colonial Countries and Peoples was intended fully to mean what the text seemed to convey, namely, that all peoples, without any discrimination, enjoy the right of self-determination.”

GA Res. 1514 (XV) of 14 December 1960.

What Are The Requirements For Secession?

For secession to be legal and successful, proof of the following must be provided:

1. identification of the group/s of people to be seceded (the "Who"),
2. the motivation for these people to secede (the "Why"),
3. Identification of the landmass area to be seceded (the "Where"),
4. that the identified areas can be controlled by a proposed system of government with formal structures and policies and will be economically feasible (the "How"),
5. that all possible internal remedies with the government of the mother country have been exhausted,
6. that the international community has been informed of the bid for freedom,
7. that there is an indisputable mandate from the people indicating their desire for self-determination (the "will of the people").