Metal detecting for treasure on public property is generally legal, according to Time magazine. However, people who use metal detectors may not claim any found object that has archaeological or historical significance, nor may they claim lost or misplaced property.
Federal laws forbid metal detecting on certain public federal lands, including national parks, national monuments, national sea shore beaches and battlefields of the Civil and Revolutionary wars, according to Metal Detecting Hobby Talk. Some states also impose restrictions on some state land, such as historical sites. Some states forbid metal detecting or require permits in state parks, while some states permit metal detecting but don't permit digging for treasure. Salt water beaches generally permit metal detecting with few restrictions, although fresh water beaches may carry more restrictions.