The invasion of Grenada by US and Caribbean troops has triggered debate among experts on international law. But the legal question is not just a technical issue for experts. The legal basis for the invasion is questioned by several nations allied with the United States as well as by a number of congressmen.
If the weight of opinion on this issue shifts against the US, then it will obviously have an impact on America's image throughout the world. Some US experts argue that legal grounds for the invasion were flimsy, and that the US has now lost the propaganda advantage it held over the Soviet Union because of the Soviet invasion of Afghanistan. Others argue that the US can make a case for the invasion based on certain provisions in the United Nations Charter and a 1981 treaty establishing the Organization of Eastern Caribbean States (OECS).
So far, the reaction from nations outside the Caribbean region has been far from encouraging to the US. Britain expressed doubts about the invasion plan. France called the invasion ''surprising'' in relation to international law. The Soviet Union, through the official Tass news agency, accused the US of seeking to intimidate ''freedom loving'' people in Latin America through a ''criminal'' action.
The White House announced that a US military aircraft carrying 61 people left Grenada Wednesday in the first evacuation of American citizens from the island. A spokesman said that other flights would follow. There are some 1,000 Americans on the island, more than half of them medical students.
In justifying the invasion, Secretary of State George P. Shultz noted on Tuesday that the OECS treaty provides for collective security. Mr. Shultz said that President Reagan decided to respond to an OECS request to intervene in Grenada, in order to protect American citizens on the island and help OECS states establish order and popularly supported governmental institutions.
Some congressmen, as well as some Europeans and Latin Americans, note the OECS is a little-known organization, whereas the better known Organization of American States (OAS) has a charter that provides that no state has the right to intervene in the affairs of another state. The US belongs to the OAS, but it does not belong to the OECS. Officials at the OAS from key Latin American nations have criticized the action in Grenada.
Rep. Michael Barnes (D) of Maryland, who chairs the House subcommittee on Western Hemisphere Affairs, has argued that the invasion raises ''some serious international legal questions.''