The rule is pretty simple but your choices in how to meet the law are not as easy as they once were. Lead shot is not legal for any kind of waterfowl hunting anywhere in the United States. The alternative, when the rule went into effect around 1990, was steel shot.Not everyone was happy with steel's performance and it could not be shot in many older, favorite shotguns. Ammunition manufacturers large and small went to work and have come up with several new types of shot that are legal in Idaho for waterfowl shooting. The legal types are listed in the waterfowl proclamation booklet.One type, bismuth shot, is advertised as safe for older guns that will not handle steel. Another, Hevi-shot, is actually heavier than lead shot and reputedly even more effective. A couple of types using tungsten have had good reviews. Steel shot has been improved in several ways, mainly by giving it higher velocity to overcome the problem of having less retained energy than other shot. The downside of the shotshells containing metals other than steel is that they are more expensive. The upside is that shotshells for waterfowling can be found to satisfy just about any need and getting the lead out is credited with saving more than two million birds every year.