Mexican President Enrique Pena Nieto has enacted a law to trace and help thousands of victims caught up in drug violence and other crimes.
The bill sets up a compensation fund and establishes a national registry to record what happened to victims.
Some 70,000 people have died in drug violence since 2006, with at least several thousand more missing.
Campaign groups say the law is a first step but needs to go further to be effective.
The legislation was passed last April but was held up after the former President, Felipe Calderon, argued that it was flawed.
But Mr Pena Nieto, who took office on 1 December, signed the bill into law on Wednesday, saying it was an important step in recognising victims' rights.
"There are thousands of people who sadly have lost a loved one, their children, their spouses, their siblings. There are thousands of people who have suffered the havoc wrought by violence," he said.
"With this law, the Mexican state hopes to give hope and comfort to victims and their families."
Under the law, relatives of people who have been killed or forcibly disappeared can claim for compensation, as well as those who have been kidnapped or injured as a result of organised crime.
Last month Attorney General Jesus Murillo said it was estimated that some 70,000 people had been killed since Mr Calderon launched a crackdown on the drug cartels in 2006. A further 9,000 were missing.
The National Human Rights Commission puts this number higher, at some 24,000.
Campaigner Javier Sicilia, who launched a peace movement following the murder of his son by suspected traffickers, said the law was a step towards justice but as with any first steps it was not enough.
Many of the families fear that the legislation will not actually be applied, a point recognised by Interior Secretary Miguel Angel Osorio Chong.
"Good laws are not enough to ensure justice. They have to be implemented," he said.
Other campaigners said the legislation in its current form was not workable, as it refers only to victims of crimes punishable at a federal level and does not define who is a victim.