Nigerian President Umaru Yar'Adua is not obliged under the constitution to write to parliament and hand power to his deputy during his absence for medical treatment, a federal high court ruled Friday. “There is no mandatory requirement for the president to make a transmission to the leadership of the National Assembly before proceeding on vacation or on treatment outside Nigeria,” Justice Dan Abutu said in his ruling at the court in the capital Abuja. But he also ruled that Vice President Goodluck Jonathan could not assume the role of acting president in Africa's most populous nation if Yar'Adua failed to make a written declaration to parliament notifying it of his absence. “That condition not having been fulfilled, the vice president cannot validly discharge the function of the president under the constitution as acting president,” Abutu said. The Senate, former heads of state and ex-ministers, the Nigerian Bar Association and the opposition have all called on Yar'Adua to formally notify parliament of his absence, a move which would allow Jonathan to become acting president. The constitution says whenever the president writes to parliament to say he is going on vacation or otherwise unable to perform his duties, the vice president takes over temporarily.