Confusing Law with Sentiment
There seems to be a crisis of conscience in South Africa at the moment, where people are incredibly loose with their interpretations of the law, using it or discounting it, depending on which argument they're trying to make. The current situation with this Chinese vessel on its way to deliver an arms shipment to Zimbabwe is a case in point.

There is no arms embargo against Zimbabwe, there are no laws against shipping arms in legal arms procurement deals between sovereign nations. As a nation, South Africa holds no right to essentially kidnap private property (the vessel) and legal product (the arms destined for Zimbabwe) because of their potential use. There is a moral issue yes, but is it ours to make?

We can unfortunately not pick and choose which laws we respect and adhere to. Trade and prosperity internationally depend on the adherence to basics of legal due process and property rights. If we don't respect Zimbabwe's property rights, how can we effectively hold a moral high ground on Mugabe's lack of respect for the property rights of his people?