A story in the Chronicle which follows up an earlier post on this topic
University of Massachusetts trustees have voted to rebuke Robert G. Mugabe but not to rescind the honorary degree UMass presented to the Zimbabwean president in 1986. According to The Boston Globe, the trustees agreed that Mr. Mugabe has presided over the ruin of his country, but concluded that they needed to establish an official policy on revoking honorary degrees before actually doing it.
Whilst it is reasonable to lack a specific policy on revoking honoraries, it does seem a little surprising that they would not have decided that they had the power to do this in any case. However, these things are far from simple.