I think most commercial aircraft have a weather radar located in the nose cone, like this:
(Source: PhotoBucket, by intelmani5)
It's well known that radar emissions can be harmful, e.g. one could get their eye burnt like an egg in a microwave oven.
However I don't know:
About the typical frequency, power and duty cycle (time in transmission mode vs time in reception mode).
Whether there is a risk for a harmful radiations exposure.
My question is: Based on current radar specifications and regulation, is there an overall ICAO (or local, e.g. US or EU) regulation forbidding the use of the radar on the ground to prevent radiation exposure for people close to the aircraft nose (or conversely to be ON at certain phases of the flight for cumulonimbus detection)?