Why unilateral acts are considered to be sources of obligations but not sources of international law? What is the difference between those two concepts

Why unilateral acts are considered to be sources of obligations but not sources of international law? What is the difference between those two concepts?

2.   Equity as source of international obligation.

3. Resolutions of international organisation as source of international obligation.

4. Comment the statement: The Court considers it beyond all dispute that a reply of this nature given by the Minister for Foreign Affairs on behalf of his Government in response to a request by the diplomatic representative of a foreign Power, in regard to a question falling within his province, is binding upon the country to which the Minister belongs (Permanent Court of International Justice, Legal Status of Eastern Greenland [Denmark v Norway], 1933).

5. Hard law and soft law.

6. Significance of foundational (main) principles of international law.

7.Notion, functions, nature of main principles of international law.

8. Peculiarities, classification and substance of main principles of international law.

9.Which of the principles enshrined in the United Nations Charter existed in international law before 1945?

10.Differences in the catalogue of the main principles of international law according to UN GA Resolution 2625 and the 1975 Helsinki Final Act.

11.Comment the statement: “In their interpretation and application the above principles are interrelated and each principle should be construed in the context of the other principles” (Resolution 2625 (XVII), Declaration on Principles of International Law Concerning Friendly Relations and Co-operation among States in Accordance with the Charter of the United Nations, 1970).