O'Neill, who was due to go to Spain, had signed an agreement that prohibits students from participating in the programme if they are on academic probation.
The protesters were demanding that the college sever links with defence contractor Raytheon Technologies which produces components for Israel’s Iron Dome.
“To lose my abroad eligibility at the last second, that was just heartbreaking,” O'Neill told the Boston Globe.
“I was practising my right as a student to speak up against the university funding a genocide.
“It just seemed, honestly, crazy and absurd to me that the university was going that far to punish me.”
Rachel Mordecai, O'Neill's faculty adviser, wrote a letter in his defence that was signed by 23 faculty members.
The statement, obtained by the Globe, called O'Neill “an exceptionally successful and talented student”.
“This denial of the opportunity to study abroad constitutes a disproportionate penalty for what Aidan participated in.”
The students say they have been left with bills of up to $20,000 for fees and travel expenses.
University spokesperson Ed Blaguszewski said: ”To participate in a UMass Amherst study abroad program, students must be in good standing academically with the university and in compliance with the university's Code of Student Conduct.
“Consistent with the university's past practice and the Student Agreement of Participation signed by each student, IPO revoked eligibility for these students to study abroad for the upcoming winter/spring terms.”
