Darting as it once was is indeed illegal. The above hunt is a vita-dart "hunt". It entails the client shooting a rhino with a dart filled with vitamins. A vet then darts it with a tranquilizer. This must be done for medical purposes only.
From SCI
Rhino Darting
The issue of darting rhinos in any form continues to swirl in South Africa. Since my article in the Safari Times last month, more clarified information has surfaced on the matter. Here is the latest information available.
Full-fledged "green" darting of a rhino by a hunting client is still illegal. This is where the hunter fires the tranquilizing dart himself. But, vita-darting of a rhino is legal if it is done under the banner of "medical purposes". The tranquilizing dart must still be fired by a licensed veterinarian, then a dart full of vitamins is immediately fired by the client. Note that the rhino must need to be tranquilized for some sort of medical purpose. This could entail blood testing, microchip implanting, the need to move the rhino to another property, or another part of the owner's property, or doctoring for an injury, etc.
Legal permits will be issued for this type of hunt by the government, once justification is determined. I have just spoken with an SCI member who participated in such a hunt with Irvin Tam within the past couple of weeks. The rhino was tranquilized, and then moved to another property. This member has the legal permits in hand.