According to the traditional approach, a state making reservation (the reserving state) can do so only with the consent of other contracting parties. The application of this principle is not difficult in the case of a bilateral treaty or with limited membership. However, it carries some problems with regard to multilateral treaties. In this case, without the consent of all the parties to a multilateral treaty, reservation will be null and void.

Error, to be a ground of invalidity, must be the one related to a fact or situation assumed by the state concerned. However if the error is related only to the wording of the text of the treaty, it cannot become a ground for the invalidation of the treaty.

Express recognition: A state may convey its decision of recognition to the new entity or government through a formal announcement, which may take the form of public statement or notification or diplomatic note or a personal message sent to the new entity. 

Implied recognition: Recognition may be inferred from the conduct of the parties involved. The act must clearly indicate that a recognizing state has a clear and inescapable intention to recognize. The intention, then, is the crucial aspect of recognition.

According to the constitutive theory, an entitybecomes a state only by virtue of recognition. It is through the act of recognition alone that a new state emerges as an international person or a new government derives the requisite authority or status in the international arena.

In contrast to the constitutive theory, the declaratory theory (also called evidentiary theory) considers that a new state or a new government exists independent of recognition. The recognition is merely an evidence of the fact that the new entity fulfils the essentials of Statehood or of a
government.

International law does not prescribe or prohibit the grant of collective recognition. States may grant recognition collectively. Collective recognition can be granted by states through some collective international act or through the medium of an international institution.

According to Article 59 of its Statute, decisions of the Court are binding upon the parties to the dispute and only in respect to that particular dispute. Under Article 94 of the UN Charter, each member of the United Nations undertakes to comply with the decision of the Court in a case to which it is a party. If the party fails to comply with the decision, the Security Council may give effect to the judgment against a recalcitrant State by making recommendations or deciding upon measures.

According to the constitutive theory, an entity becomes a state only by virtue of recognition. It is through the act of recognition alone that a new state emerges as an international person or a new government derives the requisite authority or status in the international arena. Therefore, the correct option is B.

The doctrine of non-recognition, commonly called the Stimson Doctrine of non-recognition, implies the withholding of recognition from new territorial titles or territorial changes brought out by use of force or through any other act of doubtful character. The idea behind the doctrine is not to reward a state for its unlawful acts

The most important characteristic of the international personality of an entity is its treaty-making power.

The treaty-making power of international governmental organizations is well entrenched in the United Nations practice. The 1986 Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations confirms that governmental organizations have the capacity to enter into treaties. However, their international personality is confined to their constituent instruments, resolutions, and decisions, which determine the limits of their personality. Thus, the legal personality of international organizations is now an accepted fact. However, unlike states, they do not enjoy unlimited power. Their personality, in fact, can be brought to an end by amending or terminating the constituent instruments.

Treaty contracts are the agreements between two (or only limited number of) States on a special matter concerning those States exclusively.

Sources of international law are not as explicit and accessible as those of municipal law, nor is the machinery for their identification comparable to municipal law. However, the internationally accepted classification of sources of international law is formulated in Article 38 of the Statute of the International Court of Justice. These sources are: a. international conventions, whether general or particular, establishing rules expressly recognized by the contesting States; b. international custom, as evidence of a general practice accepted as law; c. the general principles of law recognized by civilized nations; d. subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.

Monism argues that both laws are in general, components of a one bigger system. However Dualism counters that argument with accepting international law and municipal law as two different and self-contained systems. Both arguments created two further theories: Transformation (Specific adoption) Theory and Delegation Theory.

Opinio juris sive necessitatis means “an opinion of law or necessity.” It is the belief that an action was carried out because it was a legal obligation. This term is frequently used in legal proceedings as a defense in a case (USLegal).

Article 1 of the 1933 Convention on Rights and Duties of States (the Montevideo Convention) provides that “the state as a person of international law should possess the following qualifications:(a) permanent population; (b) defined territory: (c) a government; and (d) capacity to enter into relations with other States.” The correct answer is D.

In certain cases, some small states accept the protection of other states without destroying their sovereignty. Such arrangements exist for Liechtenstein (as stated above), Monaco (under the protection of France by the 1918 treaty between Monaco and France), and San Marino (under the protection of Italy). The States in this category, though under the protection of other states, are not protectorates in the sense the term is associated with the underdeveloped and exploited territories. Therefore, the correct option is D.

In recent years, many new mini states or microstates have claimed Statehood. Entities like Andorra (under the joint protection of France and Spain), Monaco (France looks after its defense and a guarantor of its sovereignty), San Marino and Liechtenstein have survived on the European scene

Treaty contracts are the agreements between two (or only limited number of ) States on a special matter concerning those States exclusively. Such treaties create obligations for the parties that would not have existed under the general international law or they modify the existing rules as applicable to their mutual relations.

Coup d’etat: sudden defeat of a government through illegal force by a small group, often a military one. Therefore, the correct option is C.

The concepts of amendment, revision, and modification connote the process of altering the provisions of treaties. Amendment is related to the individual provisions of a treaty

The Final Act of the Congress of Vienna of 1815 made Switzerland a neutral country.

Different criteria are applied in the recognition of a state and of a government. Before a new entity is recognized as a state, it should fulfil the essential attributes of Statehood as mentioned in Article 1 of the Montevideo Convention, that is, a permanent population, defined territory, a stable government, and the capacity to conduct its international relations independently. 

The Permanent Court of International Justice was created in 1921.