Wiki has it right about faculty sabbatical. Typically, you can take a full year off with half pay or half year off with full pay using funds from your home institution. Many take a full year off with half pay from their home institution and half from somewhere else (guest institution, grants etc). If a professor is said to be on leave, then, he or she is likely not paid by his/her home institution. If Shi is not paid by Princeton, then he is on leave not on sabbatical in the strict sense.

With regard to the comments by Rao Yi about transferring grants and closing labs. In Shi's case, transferring funds to China is out of the question. The solution would be to have a mechanism for Shi to keep a lab at Princeton so the research in his grants can still be carried out there and Princeton gets the overhead. It is unclear whether Princeton has (was forced?) to list him as being on sabbatical to get around some technical problems with NIH although Shi might actually be on leave. Whether Shi is in the liberty to clarify his status with Princeton becomes a bit tricky with NIH looking over their shoulders....Princeton, as a private university, differs from public ones and things are not as transparent.Certainly things can be done there that may not be strictly ethical in public universities which are under the fully scrutiny by the public.