Students holding a Colombian flag celebrate a decision of the Constitutional Court in a central street of Bogota February 26, 2010. Colombia's Constitutional Court on Friday rejected a referendum to allow President Alvaro Uribe's re-election in a ruling that ends his chance of seeking a third consecutive term in May. The decision marks the start of a tough campaign among rivals seeking to replace Uribe, who after almost eight years in power became one of the country's most popular presidents for his U.S.-backed campaign against leftist guerrillas. REUTERS/Fredy Builes (COLOMBIA - Tags: POLITICS)