Kenyan President Mwai Kibaki, centre, prepares to sign the new constitution into law, at Uhuru Park in Nairobi, Kenya, on Friday. The signing is being hailed as the most significant political event since Kenya's independence nearly a half century ago. (Khalil Senosi/Associated Press)

Kenya's president signed a new constitution into law Friday in Nairobi that institutes a U.S.-style system of checks and balances.

It has been hailed as the most significant political event since Kenya's independence nearly a half century ago.

Kenya's new constitution is part of a reform package that leaders there committed themselves to after signing a power-sharing deal in February 2008. That deal ended violence that killed more than 1,000 people after Kenya's disputed December 2007 presidential vote.

The event Friday comes after an overwhelming majority of Kenyan voters adopted the new constitution in an Aug. 4 referendum. President Mwai Kibaki's signature formally marks the end of a decades-long struggle to cut down the massive powers of the presidency.

The government and parliament now must implement the ambitious document, a process expected to take up to five years. The document requires, among other things, the formation of a supreme court and a senate.

It also demands the country's judiciary be vetted to rid it of corrupt or incompetent judges and that parliament pass 49 new laws.

However, human rights groups said the celebration was marred by the presence of Sudanese President Omar al-Bashir who faces charges of genocide and crimes against humanity in connection with violence in Darfur, where UN officials estimate 300,000 people have died.

It is only the second time al-Bashir has risked arrest by travelling to a member state of the International Criminal Court since he was first charged in 2009.