boat law question

We ran into a unhappy boater last night on the lake who was telling us it was not legal to pull a wakeboarder in a line. we normaly run a straight line in a area that there are not to many boaters and try to keep the water as smooth as possible. This guy was pulling his kides tubing which I have no problem with it is a open lake and he can enjoy his super air any way he wants. He would come by us every 20 minutes or so because he was running a gaint loop around the lake and then he stoped and told us we could not run a line that we had to do a loop because it is not legal and he would call the cops. Is there a law I have never heard this before and I thought it would be good to know. We are in Michigan and I could not find any law on the DNR listing.