Lennard,
I do not know if the coursing dogs in california use mussles. I know mussles take away from the "true sport" in most doggie mens eyes, but it can be argued that it is the "politically correct" compromise to have.
Here in Ireland, the organised official coursing meetings all have mussled dogs (as a rsult of the antis in the 1980s) and it took the wind out of the sail of the antis, and left the politicians with a compromise to satisfy both sides.
Each person has their own view on mussles, and without offending any person, coursing is still legal in Ireland where in Britiain