Sanctions
Modern Development
In former times, self-help was the primary remedy in international law. If one State breaches its obligations, the other State might take forcible and non-forcible measures to punish or counteract that breach.  This could range from war and armed reprisals to more minor confrontations.
The Covenant of the League of Nations sought to regulate war, if not entirely prohibit it. States may take self-defence in response to an armed attack, but beyond this, force is generally prohibited under modern international law.
The United Nations Charter provides a basic principle against threatening or using force in international relations. The prohibition on the use of force is a basic precept of international law from which States may not derogate.
Non-Force Countermeasures
States may take countermeasures by way of a self-help response to breaches of international law. The countermeasures may be taken by an international organisation on a multilateral basis. The issues of non-forcible reprisal and economic sanction raise questions of credibility with international law.
Lawful non-forcible measures may be taken under international law. Countermeasures may allow injured state parties to vindicate their rights and restore the legal position which has been ruptured by an unlawful act.
Non-forcible countermeasures may only be taken in response to an internationally wrongful act and only against a State responsible for the act. They are limited to temporary non-performance of international obligations owed to the injured party by the responsible State.
Under the ILC Articles on States Responsibility 2001 countermeasures are instruments for achieving compliance with obligations. They are intended to induce rather than to punish. They should be proportional and used only to the extent necessary.
Justifying Countermeasures
The breach by one State of its obligations is the justification for the suspension of an obligation which would otherwise be a breach of international law. Countermeasures may be unilateral by way of a suspension of a trade agreement or freezing of assets. Countermeasures may typically involve the suspension of international obligations.
If a situation arises in one State\’s view that results in a violation of an international obligation by the other, the first State is entitled within the general rules of international law to take countermeasures.
International tribunals and courts will review the extent to which countermeasures are justifiable. This leads to the difficulty that countermeasures are taken by the subjective act or in accordance with its own subjective view of the position in the first instance.
Countermeasures do not equate to the suspension or termination of treaty obligations due to material breach within the meaning of the Vienna Convention on the Law of Treaty. The suspension or the termination of a Treaty may affect the legal obligations of States. However, in contrast, countermeasures deal with responsibility arising by reason of breach and seek to rectify a temporary breach.
Retorsion
Retorsion is something done by one state on another in retaliation for a similar act done by the other state. It might be the use of comparably severe measures against citizens of the other state within the borders of the retaliating state when the other state has done in similar acts.[
Retorsion is in contrast to reprisal.Reprisals are illegal if their purpose is punishment or coercion of the sovereign. A Â retorsion is, by definition, something in conformity with international law, even if it is an unfriendly act.
Material Breach
The Vienna Convention on the Law of Treaties deals with a material breach of a Treaty. Countermeasures may be taken in response to a breach, provided they are proportionate.
The VCLT provides a procedure for suspension or termination of Treaty obligations for material breach, which differ from countermeasures.  The former must be confined to the Treaty being breached, whereas countermeasures are not so limited.
There is no reason, in principle, why countermeasures could not be taken against an international organisation. They apply in principle to entities with international, legal personality.
Measures which punish the responsible State are termed retortions. They are not limited to the suspension of international obligations owed to the responsible State. Acts of retorsion may include, for example, limitation of normal diplomatic relations, embargos and withdrawal of aid programs.
Justifying Countermeasures
The International Court of Justice may consider the legality of countermeasures and will focus particularly on their proportionality.
Countermeasures more typically may take the form of suspension of a trade agreement; the acts of retortion are based on the freedom to trade or not to trade. They are unfriendly but lawful acts.
Countermeasures must be retaliatory. They must occur after the breach. They cannot be anticipated. They must be based on the occurrence of an unlawful or unfriendly act. Countermeasures should be temporary and aimed at the responsible State. They should be reversible so that relations can be restored.
A countermeasure must be proportionate to the gravity of the injury suffered. A state which engages in disproportionate countermeasures itself incurs State responsibility. A weaker State should be subject to quantitatively less countermeasures than would be proportionate in respect of a powerful State.
Countermeasures Nature
Countermeasures must not violate basic obligations, including those in relation to human rights, humanitarian obligations and use of force. They should not affect dispute resolution procedures that apply. They cannot interfere with diplomatic or consular immunity.
Countermeasures should follow an unsatisfied demand on the state responsible for complying with its international obligation. Prior notice should be given except in cases of urgency where it is necessary to proceed without notice to preserve the state\’s rights.
Collective
Countermeasures are generally taken by the state which has been injured by the wrongful act of another. In some cases, however, third-party states may take action in the collective interest.
This arises as a result of the breach of obligations owed generally, including, for example, human rights obligations, genocide aggressions, slavery, racial discrimination, self-determination and other infringements of basic principles of international law owed to all States.
There may be collective countermeasures, though in essence, they are concurrent individual initiatives. The UN Security Council may impose sanctions through certain machinery. This may complement multilateral countermeasures.
International organisations such as the EU and individual States as well as the UN Security Council have imposed trade sanctions in response to acts of aggression, apartheid, and genocide as well as repression of democracy.
Countermeasures may involve suspension of existing international law obligations or Treaty obligations. Some sanctions have taken the form of removal of civil aviation landing rights. Freezing of assets have been a response to breaches of fundamental norms.
Mandated by Organisation
In some cases, the embargo may be in accordance with the rules of a particular institution, such as the Security Council or EU. In other cases, it involves the suspension of Treaties based on the breach. In practice, there may be an overlap of rationales or basis on which sanctions on countermeasures are based.
Groups of states may take actions outside the Security Council where they have been unable to secure Security Council support.
It may be that a complaint should be brought before an international organisation first as a precondition to any unilateral countermeasures or sanctions. In these cases, the treaty in effect, requires that wrongdoing must be responded to in a collective manner, if possible.
International organisations and states may take countermeasures without seeking the authority of the Security Council. If the UN Security Council proceeds to take non-forcible measures after determining that a situation of aggravated responsibility is also a threat to peace, the Charter provides that the UN Security Council takes over and individual States may only take action to the extent allowed by the UN Charter, individual or collective self-defence or it is recommended or decided on by the Security Council.
Unilateral Measures
There is an increasing trend towards collective, non-forcible measures for breach of international norms. However, unilateral measures still remain possible beyond the countermeasures.
On some views, this is permitted only when organisational routes have been exhausted. It is suggested that in this context, retorsion is lawful as a remedy but that non-forcible reprisals are unlawful where there is a punitive element.
Powerful States such as the US have imposed unilateral measures when Security Council sanctions have not been available for political reasons. During the Cold War in particular, countermeasures and sanctions were frequently political in nature, seeking to pursue political objectives.
The US has imposed sanctions on a number of States, including Sudan, Somalia, Iraq, parts of Angola.The US has taken the view in relation to Cuba that the right to trade is a matter of national sovereignty.
Accordingly, it has justified economic embargos on largely political grounds. It considers that non-forcible economic coercion may include trade, financial, commercial, and arms embargoes.
It is argued that the US measures go far beyond permissible countermeasures and amount to coercion.
Sanctions
Punitive measures of coercion which forces the responsible State to stop its acts might be termed sanctions.
Sanctions in international law are indeterminable and less systematic than under national law. Apart from sanctions by institutions, there are individual state sanctions by way of self-help. There is no central law-enforcing agency. Enforcement may be largely political in nature.
Sanctions in the sense commonly used are specific measures. A countermeasure is temporary and is intended to be coercive. A sanction is final in its nature and is more likely to be punitive.
Unilateral sanctions are generally unlawful in this sense. In order to be lawful, they must be undertaken by an international organisation representing centralised mechanisms. According to this view, the sanctions should be imposed by a competent organisation in accordance with its procedures.
UN Security Council
The UN  Security Council may impose total or partial trade, financial, and commercial sanctions, and arms embargoes. The scope is broad enough and may include most kinds of punitive action short of armed force.
The Security Council is required by the UN Charter to determine whether there is a threat to peace, breach of the peace or act of aggression. Economic measures may be provided under the UN Charter.
Sanctions aimed to achieve regime change are unlikely to be lawful if undertaken unilaterally. Regional sanctions as collective sanctions may be within the scope of international law. The articles on the Security Council and the sanctions purport to prevail over other international obligations.
The UN may impose sanctions for the purpose of restoring peace and security. Sanctions should be proportionate. It must not cause serious violations of human rights. They must be proportionate to the interest protected.
Since the beginning of the millennium, sanctions have become more targeted. Sometimes leaders of a regime and non-state actors are sanctioned.