There was one notable — and loudly noted — absence at Columbia University’s graduation ceremony: detained pro-Palestinian student protest leader Mahmoud Khalil.

“Boo… Shame on you!” students chanted when Clare Shipman, interim president of the prestigious New York City school, took the podium.

That didn’t prevent chants of “Free Mahmoud.”

Some students wore keffiyehs as scarves or in lieu of graduation caps, donning a symbol of the Palestinian cause.

“We firmly believe that our international students have the same rights to freedom of speech as everyone else, and they should not be targeted by the government for exercising that right,” Shipman said.

“And let me also say that I know many in our community today are mourning the absence of our graduate, Mahmoud Khalil,” she added before launching into a plea to defend democracy, which she described as “the essential work of your generation.”

Columbia students have reported a chill to campus free speech and a sense of shame that their university did not do more to support freedom of expression.

One held a sign that read: “There is no graduation in Gaza today. “