I can't see a definitive response to your question.
The answer is YES.
Note that this thread was started in 2008. Definitive answers were given at that time.
I can confirm that the official line has not changed since then - PLs are only permitted on closely mown areas.
However, in more recent (2015) correspondence with the R&A re the use being made by the PGA Tour, they said their view was now more relaxed.
"That said, and we cannot stress this strongly enough, obviously this should be used sparingly and only where absolutely necessary, e.g. to facilitate play in the winter. If a course is having to do this at other times of the year there is probably an agronomy/course maintenance problem. Using such a Local Rule will probably affect the qualifying status of competitions held on the course…we are not a handicapping body though and cannot advise on that."
The last point certainly affects CONGU and the European Golf Association handicapping systems. I don't know about GA.
Edited by AAA, 14 April 2018 - 05:24 PM.