From Peter Suderman's post on Reason's Hit & Run:
Under the umbrella of the Americans with Disabilities Act, the federal government has issued new regulations governing the size, slope, and even the length of the grass fibers used on the course. Via Ryan Young of the Competitive Enterprise Institute :
The federal government regulates the slopes of miniature golf courses. The new standard “permits a slope of 1:4 maximum for a 4 inch rise where the accessible route is located on the playing surface of a hole.”
If a course uses artificial turf instead of grass, it also regulates length for the fibers. The height of the “grass” shall not exceed half an inch.
The so-called “start of play” areas must be at least 48” x 60”, and shall not have a slope steeper than 1:48.