Gretna's "runaway marriages" began in 1754 when Lord Hardwicke's Marriage Act came into force in England. Under the Act, if a parent of a person under the age of 21 objected to the minor's marriage, the parent could legally veto the union.
The Act did not apply in Scotland, where it was possible for boys to marry at 14 and girls at 12 with or without parental consent.