Launching into a fiery speech, the head of the Syrian National Coalition Ahmed Moaz al-Khatib demanded that the opposition be allowed to represent Syria at the United Nations and insisted that Syrians would determine their own future.
Khatib, who threw the opposition into disarray by announcing his resignation on Sunday, led the Coalition delegation into the hall at the invitation of Qatar Emir Sheikh Hamad bin Khalifa Al-Thani, who opened the summit.
The rebel flag replaced the official Syrian bunting as Khatib accompanied by Syria's first rebel prime minister Ghassan Hitto and other opposition leaders took their seats.
There had been confusion over whether the delegation would be headed by Khatib or by Hitto, in the wake of the Coalition leader's resignation.
But Khatib made it clear he was still firmly at the helm of the opposition.
"We demand all forms of support from out friends and brothers including our full right for self-defence and the seat of Syria at the United Nations and at other international organisations," he told the summit.
He also stressed that the Syrian people alone would determine the future of their country.
"They ask who will rule Syria. The people of Syria will decide, not any other state in this world," Khatib said, possibly alluding to accusations by Damascus that the rebels are implementing Qatari and Saudi agendas.
"The Syrian people's decisions are based on its interests. It rejects any foreign mandates," he said.
The Qatari hosts, the most vocal supporters of the revolt against President Bashar al-Assad, had won the promotion of Syria's opposition National Coalition to fill Syrian position.
The seat has been empty since the Arab League suspended Syria's membership in November 2011 after Damascus rejected an Arab proposal to end violence against protesters and instead pressed a bloody crackdown on dissent.
The Arab Spring-inspired protests morphed into an armed rebellion against Assad's regime and later into a civil war in which more than 70,000 people have been killed so far, according to UN figures.
The decision to hand the seat to the opposition has not been without its detractors, with reservations expressed by Iraq, Algeria and Lebanon.
Damascus reacted furiously to the decision of the 22-member grouping.
"Shame on you, Arab brothers," wrote Tishreen state-owned daily, branding the Arab League decision as a "theft".
"This theft that the sheikhdom of Qatar and other collaborator, treacherous, backward Arab regimes have committed by handing the Doha-sponsored Coalition the Syrian state's membership is a legal, political and moral crime," it said.
On Monday, Al-Thawra government-owned daily charged the "League has handed Syria's stolen seat to bandits and thugs." "They have forgotten that it is the people who grant the powers and not the emirs of obscurantism and sand," it said, a clear reference to Qatar and Saudi Arabia.
Khatib in his address made no mention of his resignation, but ahead of the summit he had said it would be dealt with after the meeting is over. The coalition has yet to accept his resignation.
An opposition source told AFP that Khatib had accused "certain countries, notably Qatar, of wanting to control the opposition" and of having imposed Hitto as premier.
Khatib in his speech on Tuesday pointedly expressed his confidence in Hitto. "We trust him. The general assembly of the coalition awaits his programme to debate it," he said.