Nope, see below from DNR website… The last paragraph pretty much sums it up as illegal
Is it environmentally OK for my neighbors to rake their leaves into the lake to dispose of them?
The DNR highly discourages individuals from dumping their leaves and grass clippings into a lake, river, or wetland. In addition, this material should not be raked into the street where it can wash into the storm sewer that drains to water bodies or watercourses. Leaves and grass clippings add nutrients that use up valuable oxygen as they decompose, on which aquatic organisms in the food chain depend. The DNR encourages good stewardship of our water and land resources. There are alternative stewardship practices for disposing of leaf and grass clippings that are more environmentally friendly. The best way to dispose of this waste is to compost it either on your land or at a designated compost site in your community. An excellent source of information on the environmental benefits of proper leaf disposal is a DNR publication entitled “Lakescaping For Wildlife and Water Quality” available from Minnesota’s Bookstore.
Reports of pollution or littering in public waters or public waters wetlands should be referred to the local DNR conservation officer, Minnesota Pollution Control Agency, and county officials such as sanitarian or sheriff.