President Barack Obama told PBS’ NewsHour last week that he was convinced chemical weapons had been used in Syria’s civil war by the country’s regime. The assumptions he made to reach that conclusion are dubious.

“We have looked at all the evidence and we do not believe the opposition possessed chemical weapons of that sort,” the president said. “We do not believe that, given the delivery systems, using rockets, that the opposition could have carried out these attacks.”

There is no doubt that Syria’s government has chemical weapons. It is, in fact, suspected of possessing hundreds of tons of mustard gas and large stockpiles of sarin gas, possibly VX, both of which are nerve agents.

But delivering such weapons is far from complicated. Even fairly antiquated artillery can be used, besides aircraft and missiles, to disperse poison gasses. Syrian opposition fighters have been seen possessing artillery that could be used to fire a nerve agent into a neighborhood from a close distance.

Whether rebels also possess chemical weapons is unclear. The Washington Post reported last year that rebels had seized a military installation near Aleppo “where research on chemical weapons had been conducted.” A Syrian army defector told the same newspaper that other chemical weapons sites weren’t secure either. “Probably anyone from the Free Syrian Army or any Islamic extremist group could take them over,” he said.

Turkey’s Zaman newspaper reported earlier this year that security forces had seized two kilograms of sarin gas in the city of Adana in southern Turkey. “The chemical weapons were in the possession of Al Nusra terrorists believed to have been heading for Syria,” it said. Obviously, they didn’t manage to smuggle the gas across the border but others may well have been successful.

There is also the possibility that jihadists, who flocked to Syria to fight a religious war there, gathered chemical weapons in Libya after its strongman, Muammar Gaddafi, was deposed and murdered in late 2011.

The Nuclear Threat Initiative’s Global Security Newswire cited a story in The Wall Street Journal saying an ammunition complex in the desert near Sirte was left unsecured after government forces were defeated, “allowing looters to walk in and steal guided missiles, rockets and artillery shells capable of dispersing chemical warfare agents.” Britain’s The Telegraph later reported Spanish concerns that terrorists “could have acquired” chemical weapons “in Libya or elsewhere.”

None of the newspaper coverage has been conclusive except for a story in MintPress News published last week that quotes residents of Damascus and Ghouta, the suburb where hundreds of civilians were apparently gassed, blaming the opposition.

Many believe that certain rebels received chemical weapons via the Saudi intelligence chief, Prince Bandar bin Sultan, and were responsible for carrying out the dealing gas attack.

Saudi Arabia has long backed the Syrian uprising with arms and money. The kingdom has both a sectarian and strategic imperative in hastening President Bashar Assad’s demise. The rebellion against his regime is largely composed of Sunni Muslims, the majority population in Syria that suffered repression under Assad’s Alawite rule. Saudi Arabia seeks a leadership role in the Sunni Muslim world. Assad is also the only Arab ally of Saudi Arabia’s nemesis Iran.

The Wall Street Journal last month described Bandar as “a veteran of diplomatic intrigues” who was “jetting from covert command centers near the Syrian frontlines to the Elysée Palace in Paris and the Kremlin in Moscow,” capable of delivering “what the CIA couldn’t: planeloads of money and arms.”

A former ambassador to the United States, Bandar was appointed head of Saudi intelligence last year after spending almost a decade out of the public’s view. He now seems in charge of the Saudi effort to topple Assad.

Syria’s deputy foreign minister implicitly accused Saudi Arabia of orchestrating the chemical weapons attack when he told Euronews that radical Islamists, armed and financed by the oil kingdom, were “responsible for the bloodshed in Syria. Saudi Arabia is the main player.”

Unlike Assad, who was warned by Obama last year that the use of chemical weapons on his part would cross a “red line,” the rebels had an incentive to deploy poison gas: to trigger exactly the sort of retaliation the United States are now contemplating. A military strike against Assad’s forces could help tilt the balance of the war in the insurgents’ favor.