Pakistan President Asif Ali Zardari's has signed an accord to put part of the country under Islamic law as part of efforts to end a Taliban insurgency in the region.
President Zardari's move formalises a controversial deal between a pro-Taliban cleric and the government in North West Frontier Province.
The cleric led thousands of supporters to fight against US troops in Afghanistan in recent years.
The deal applies to Malakand, a district of around 3m people in the province that includes the Swat valley.
The central government lost control in Swat, a former ski resort and jewel in the crown of Pakistani tourism, after cleric Maulana Fazlullah launched a campaign to enforce Taliban-style Sharia Law.
Militants beheaded opponents, bombed schools and fought government forces, prompting tens of thousands of people to flee.
'God willing it will have a positive impact on the situation in Swat,' said interior ministry chief Rehman Malik of the agreement.
'It is hoped that those who wanted this law in Swat will now surrender their arms and also bring the peace,' he told reporters.
However, critics say the deal opens the floodgates to the 'Talibanisation' of swathes of Pakistan, and the policy came under widespread criticism when a video emerged earlier this month of a veiled woman being flogged in public.
A spokesman for pro-Taliban cleric Soofi Mohammad, who signed the accord, said Mr Zardari's signature would allow peace in Swat, just 160km away from the capital Islamabad.
