In 2007, Parliament elected Gul for one-time term as president, but a few months later Turkey enacted constitutional changes that allowed the election of presidents in popular votes for a five-year term.
Friday's ruling could have wider political implications because it comes at a time when a debate is under way in Turkey about whether it should switch to a system where the president, not the prime minister, is the top elected official.
The Constitutional Court said Friday that Gul, 61, can stand for re-election in 2014. The president cannot serve more than twice. Currently, the Turkish presidency has some veto authority but is largely removed from daily politics.
Prime Minister Recep Tayyip Erdogan, who won a third four-year term in 2011, says the country should shift to a presidential system, despite worry by some Turks that Erdogan, 58, would seek the post and continue in power.
A presidential system could, in theory, contribute to democracy by dispersing power in Turkey, where the prime minister commands the unswerving loyalty of hand-picked legislators and the administration oversees the budget.
Some commentators fear Erdogan would balk at the checks and balances of a U.S.-style presidency, fashioning instead a system closer to the model in Venezuela, where President Hugo Chavez has broad powers.
"A president would be stronger if he maintains ties to his party," Erdogan said in an interview with ATV television last week. "A further step should be taken to get more successful results for our country; it could be either a presidential or a semi-presidential system."
Erdogan, a charismatic and popular leader, said a presidential system can transform what he called a "double-headed structure into single-head."
Deputy Prime Minister Besir Atalay said Friday that Turkey should debate a shift to presidential system "without hesitation and fear.
Gul, a long-time ally of Erdogan, is not expected to stand for re-election as president. At this point, Erdogan will not be able to run for Parliament in the next election in 2015 since his party bars running for a fourth consecutive term.
Gul and Erdogan had swapped power in the past. Gul served as prime minister for four months before Erdogan's political ban was lifted after their Justice and Development Party came to power in late 2002.
Erdogan had been banned from politics and served a four-month jail sentence in 1999 for inciting hatred based on religious differences, by reading a poem at a political rally. The poem said: "Minarets are our bayonets, domes are our helmets, mosques are our barracks, believers are our soldiers."
The debate over a presidential system highlights concerns within the secular establishment, which resents Erdogan's domineering style of leadership and the Muslim character of his government.
Under Erdogan, the government has reduced the political clout of the military and steered Turkey toward strong economic growth and a higher diplomatic profile in the region. His government is now trying revive the country's stalled bid to join the European Union.
Associated Press writer Emrah Betos contributed to this report.