Colombian has enacted a controversial law that aims to compensate an estimated four million victims of the country's long-running armed conflict.
The Victims' Law, described by President Juan Manuel Santos as "historic", allows damages to be paid to relatives of those killed.
It also seeks to restore millions of hectares of stolen land to its rightful owners.
Analysts say implementing the law is a huge challenge that may take a decade.
Marxist rebels continue their 47-year struggle to overthrow the government, while drug cartels ship hundreds of tonnes of cocaine out of the country, using the billions of dollars of earnings to undermine the state.
Violent response fears
The BBC correspondent in Colombia, Jeremy McDermott, says the compensation bill could total $20bn (£12.3bn).
He says that is a sum of money that the country just does not have at the moment.
United Nations Secretary General Ban Ki-moon, who attended the signing ceremony in the capital Bogota, described the law as an "important advance" for Colombia.
But he cautioned that the work had only just begun, and promised that the UN would help Colombia implement the legislation.
Last month, the Colombian government said owners had lost nearly seven million hectares (17m acres) of land over the past 25 years of armed conflict.
Agriculture Minister Juan Camilo Restrepo said paramilitaries, rebels and drug traffickers had used a mixture of violence and fraud to take control of land, which had made them immensely rich.
Some armed groups - which still occupy much of the stolen land - have already tried to undermine the process.
There are fears that they will respond violently to attempts by the rightful owners or the state to repossess the land.
On Tuesday, a campaigner for land restitution, Ana Fabricia Cordoba, was shot dead in the city of Medellin.