"Traditional slavery is the oldest, the oldest slavery which the world has known, and this slavery is a product of inheritance," he said. "All the slaves that we have here today are slaves from the ancestors, their parents, their grandparents. They are slaves of inheritance."
In Ioukhede's case, her master's son inherited her. "I do the same work that my parents did for my master."
She has five children, two boys and three girls, and they all also belong to her master.
Cachiolli says that children are taken away from their mothers to destroy the family links so slaves don't really know who their ancestors are. "As you can imagine in Africa, that's a very important tradition, to know who your parents are, so that's how slavery is perpetuated," she said.
One Muslim holy man explains Niger's slave policy as a religious phenomena.
"According to the Koran, a slave is a person who refuses to become a Muslim," said Al-aji Idriss Abandaba, Imam of Niamey. "This means that if you are a Muslim you cannot be a slave."
But critics say slavery has been around a lot longer than Islam and that the arrival of religion did nothing to break the chains of tradition. Some masters may even be accused of using religion as a way to brainwash their slaves and control them.
"Islam assisted in the indoctrination of slaves through the use of religion, by saying for example if you disobey your master, you will not access paradise, hence your paradise is in the hands of your master," said Weila.
Slaveholders' dominance may be waning, however.
"Slavery is a state of an individual on which is practiced attributes the rights of ownership, it's a human being who is the object of another," said Masouse-a-Damou, the secretary general and minister of justice of Niger, reading from the text of a new anti-slavery law.
Before this law was enacted, slaves did not technically exist. They were non-people, they weren't even defined in the legal system, but with the help of lawyers like Chebou Abdoura Hamam, Ioukhede is now recognized as a citizen and a person.
"The slave is someone who has been molded for generations, that is a form of fatalism, they have accepted their status," said Abdoura Hamam. "They think that it is God that says that we are born slaves, so there is no need to fight against it.
According to the Ministry of Justice, it's a criminal offense to reduce a human to slavery in Niger, punishable by law with a minimum sentence of 10 years to a maximum of 30 years.
Enacting the law criminalizing slavery is the first step, but applying it is a different matter. Many of the government ministers are from slaveholders' families, and are being lobbied hard by the traditional leaders to protect the status quo. In April, the government of Niger announced that slavery no longer existed.
But slaveholders are still clinging to their "inheritance," and have more or less disregarded the new law.
Worse still, the slaves have now lost their key campaigner and defendant. Weila was arrested and imprisoned at the end of April on charges of fraudulently trying to raise money from Anti-Slavery International. The nongovernmental organization denies the allegations. Weila has been refused bail and no date has been set for his trial.
Cachiolli says Weila is guilty of one thing: he lifted the lid on slavery in Niger. "The authorities are now very irritated that so much international attention is now being focused on Niger, particularly slavery in Niger," she said.
If you would like more information about slavery in Niger and around the world, Click Here.
ABC News' Oliver Steeds filed this report for "Nightline."