Prior to the Apollo 11 mission, NASA administrator Thomas O. Paine appointed a committee to discuss what would be an appropriate and meaningful item or items to leave on the moon to mark the first human visit.
It is reported that he sternly reminded them not to allow the symbolic gesture get in the way of crew safety or training, and to minimize the weight and space requirements. Oh, and by the way, don’t violate the Outer Space Treaty!
Outer Space Treaty? Yep, we had one. In 1967, the treaty stated that no nation can claim territory in space. All signatory nations agreed to abandon the old days of planting flags on islands and declaring it a colonial possession.
Administrator Paine would avoid at all costs giving the impression of the U.S. had won the race to the Moon, therefore claiming the Moon as the 51st state. However, he did want to mark the first lunar landing an historic step forward for all mankind, which would be accomplished by the United States of America.
He agreed to go forward with the planting of the U.S. flag. So, NASA braced itself for the international community to take exception to the flag raising as a violation of the 1967 Outer Space Treaty.
That backlash never came.
In November 1969, Congress passed a law stating that the American flag would be placed on every moon, planet or asteroid astronauts might land on in the future, as long as the mission had been solely funded by the U.S. government.
Also clarified in the new law, it stated, “this act is intended as a symbolic gesture of national pride in achievement and is not to be construed as a declaration of national appropriation by claim of sovereignty.”