If you look at the Moon through a telescope, you will immediately notice that much of its surface is covered by craters. Some of these may be volcanic in origin, but many or most are meteorite craters and they were made when cosmic debris from elsewhere — most likely the asteroid belt — crashed into the Moon. When the composition of a lunar meteorite that has been found on Earth is analyzed in the laboratory, it is clearly seen to be a match for specimens transported to Earth by the Apollo astronauts. More remarkable than that, even, is the fact that some lunar meteorites can be paired with a particular part of our nearest neighbor, meaning we can tell not just that they came from the moon, but also which part of the Moon!
While it is illegal for private collectors to own Apollo return samples, it is entirely legal to buy lunar meteorites. These specimens have been analyzed and authenticated by leading meteorite scientists and are, without a shadow of a doubt, authentic and legitimate geological examples of our nearest celestial neighbor.