Clean. Dry. Inspect.
Yellowstone National Park recently announced in a press release that felt sole boots are now banned in the park starting immediately. While there is some disagreement on whether or not rubber soles actually help prevent the transportation of aquatic invasive species (AIS), YNP feels that by banning felt this will help stop the spread or introduction the Yellowstone's fabled trout waters.
Anglers need to clean, dry, and inspect boots and waders before entering YNP waters and realistically should be doing that before they fish new waters anywhere in the country. In addition to the felt sole ban there are new regulations and seasons for boating in Yellowstone which includes small watercraft such as float tubes.
For the full press release and information please refer to Yellowstone National Park's website: https://www.nps.gov/yell/learn/news/18010.htm