When U.S. forces landed on Grenada five days ago, one of their prime objectives was to secure the person of Sir Paul Scoon, who has become key to an elaborate legal justification for the invasion and appointment of a new government.

U.S. armored cars rolled up to Scoon's residence overlooking the capital of St. George's on Wednesday. U.S. troops quickly freed him--apparently without violence--from Cuban or Grenadan soldiers and put him aboard a helicopter to the aircraft carrier Guam offshore.

According to officials of the U.S. and Caribbean governments whose troops now occupy Grenada, Scoon, 48, is to be the island's new leader. But Grenada's 110,000 people are still waiting to hear from him directly about his plans.

Radio Free Grenada, the island's official voice, was supposed to return to the air with an address from Scoon Thursday, but it has remained silent.

Since 1978, Scoon, a bespectacled tennis-playing man who taught at a boys' school on the island for 13 years, has served as Grenada's governor general, the official link to the British monarchy and a largely ceremonial post in Commonwealth countries. An obscure figure previously, he suddenly leaped into the international limelight.

Caribbean leaders who joined the United States in sending troops say that Scoon, shocked by the bloodshed that followed a military coup d'etat two weeks ago, conveyed abroad a secret plea for military action before the invasion.

The United States and its Caribbean allies now recognize him as the sole legitimate political authority on the island and have asked Scoon, a Grenadan citizen, to form an interim government pending elections.

On Friday, Scoon telephoned Buckingham Palace--Queen Elizabeth was reported to be "glad" that Scoon, his wife and three children were safe--and United Nations Secretary General Javier Perez de Cuellar.

He told Perez de Cuellar that he planned to close Grenadan missions abroad pending formation of a new government and hoped to conduct elections within six months.

Today he conferred in St. George's with U.S. Ambassador Milan Bish and Barbados' Prime Minister Tom Adams.

Jamaican Prime Minister Edward Seaga arrived here this afternoon for a meeting of leaders of Caribbean countries with troops in Grenada.

Seaga criticized British Prime Minister Margaret Thatcher for her condemnation of the invasion, a stance which he said marked the end of British influence in the Caribbean.

Speculation in Barbados has it that the delay in Scoon's maiden address to Grenada could be related to official displeasure in London, where the government has condemned the invasion and might resent the political uses to which Washington and the Caribbean states are putting the Crown's man on the scene.

Scoon's role in Grenada's crisis has refocused attention on murky areas of Commonwealth law concerning the authority of governors general.

A Buckingham Palace spokesman has said that Scoon has a "constitutional right" to form a new government.

Grenada, like many former British colonies, elected to retain the British monarch as head of state after it achieved independence in 1974. The governor general would be nominated by the local government but appointed by the queen.

Scoon, who received the knighthood that generally goes with the job, was nominated by Eric Gairy, the eccentric, pro-western prime minister whom Maurice Bishop overthrew in 1979. Bishop proceeded to forge close ties with Cuba and the Soviet Union but made no moves to sever Grenada's ties to the Commonwealth or to unseat Scoon.

Under the Grenadan constitution, which Bishop suspended shortly after he took power, the governor general was empowered to dissolve Parliament at the request of the prime minister and to appoint a new cabinet in extraordinary crisis conditions.

In practice, however, he had a scant political role. Occupying a spacious official residence, his functions centered on raising the toast glass at national day celebrations, receiving visiting dignitaries and signing documents drafted by the government.

Adams has said that after Bishop and several of his top aides died at the hands of a military council led by Gen. Hudson Austin, Scoon's views on intervention were sought through an intermediary from an unknown third country. According to Adams, "Sir Paul agreed" to request intervention "as soon as possible."

After Scoon was reached by U.S. forces, according to Adams, he put his pre-invasion request in writing in the form of a letter delivered to the head of the joint Carribean force asking for help in "stabilizing this grave and dangerous situation."