By Tim Hirsch
BBC News, Sao Paulo
Brazil's government says it wants to protect the rainforest
Brazilian President Luiz Inacio Lula da Silva has approved a controversial bill allowing Amazon farmers to acquire an area of public land larger than France.
But the president vetoed some of the most contentious clauses that would have enabled absentee landlords and companies to benefit from the measure.
Smaller parcels of public land will be handed over for free, and larger ones at reduced or market rates.
Critics say it will amount to an amnesty for illegal land-grabbers.
The law is intended to end the chaotic state of land occupation in the Amazon.
Hundreds of thousands of farmers have no legal title over their land, with claims often dating back decades.
President Lula vetoed changes to the bill made during its passage through congress, which he claims would have altered the original aim to benefit smaller farmers.
But he has left in a clause that allows larger properties to be sold on within three years, instead of requiring the new owner to hold on to the land for at least a decade.
Environmental groups fear that could lead to a heating up of land speculation in the Amazon and encourage occupation of new forest areas.
Among the critics of the measure have been federal prosecutors in the Amazon, who claim it is unconstitutional because it enables land to be given to people who have acquired it illegally, and because it could infringe the rights of traditional and indigenous communities.