"I say to the foreign secretary, I say to the prime minister, where is the legal basis for this?" Corbyn said.
"The legal basis… would have to be self defence or the authority of the UN Security Council. The humanitarian intervention is a legally debatable concept at the present time," he said in an interview with the BBC.
He added that if there is evidence that Syria's Assad used chemical weapons against his own people, British government must demand answers from him.
"I think parliament should have a say in this, and the prime minister could quite easily have done that… She could have recalled parliament last week … or she could have delayed until tomorrow when the parliament returns itself … What we need in this country is something more robust, like a war powers act, so that governments do get held to account by parliament for what they do in our name," he said.
Earlier, Jeremy Corbyn stated that the UK should be playing a leadership role to bring about a ceasefire in the conflict, and that it shouldn't take instructions from Washington or put British military personnel in harm's way.
According to the Russian Defense Ministry, the three countries fired over 100 cruise as well as air-to-surface missiles.
The Syrian Foreign Ministry has slammed the joint US, British and French strikes as a "brutal, barbaric aggression," saying that the attack "aims at hindering the OPCW Organization for the Prohibition of Chemical Weapons mission's work and preempting its results."