Legality
The US government invoked self-defense as legal justification for its invasion of Panama.[46] A number of scholars and observers have concluded that the invasion was illegal under international law. The justifications for invading given by the U.S. were, according to these authorities, factually baseless, and moreover, even if they had been true they would have provided inadequate support for the invasion under international law.[47] Article 2 of the United Nations Charter, a cornerstone of international law, prohibits the use of force by member states to settle disputes except in self-defense or when authorized by the United Nations Security Council. Articles 18 and 20 of the Charter of the Organization of American States, written in part in reaction to the history of US military interventions in Central America, also explicitly prohibit the use of force by member states: "[n]o state or group of states has the right to intervene, directly or indirectly, for any reason whatever, in the internal affairs of any other state." (Charter of the Organization of American States (OAS), Article 18.) Article 20 of the OAS Charter states that "the territory of a states is inviolable; it may not be the object, even temporarily, of military occupation or of other measures of force taken by another state, directly or indirectly, on any grounds whatever."[48] The US has ratified the UN Charter and the OAS Charter and therefore they are among the highest law of the land in the US under the Supremacy Clause of the US Constitution. Other international law experts who have examined the legal justification of the US invasion have concluded that it was a "gross violation" of international law.[49]
The United Nations General Assembly passed a resolution strongly deploring the 1989 U.S. armed invasion of Panama. The resolution determined that the U.S. invasion was a "flagrant violation of international law."[50] A similar resolution proposed in the United Nations Security Council was supported by the majority of the Security Council but was vetoed by the US and two of its closest allies.[51]
Independent experts and observers have concluded that the US invasion of Panama also exceeded the authority of the president under the US Constitution because Article I, Section 8 of the Constitution grants the power to declare war solely to the Congress, not to the president.[52] [53] According to observers, the US invasion also violated the War Powers Resolution[54], a federal law designed to limit presidential action without Congressional authorization, because the president failed to consult with Congress regarding the invasion of Panama prior to the invasion.[55] [56][57]