Swaziland's King Mswati III has made it illegal for anyone under 18 years of age to get married.
The law is aimed at preventing under-age marriages, of which, many young girls were either kidnapped or forced into marriage, often with no other choice.
But child rights group Save the Children says that chiefs are already arguing against it.
The tribal leaders feel that the law should only apply to "Western-style" marriages, not traditional ones.
Al Jazeera's Tania Page reports from Swaziland.