First, the remains of a cremated body are not “ashes,” as the term is commonly referred to. The remains are bone fragments that, can be too large to scatter if they have not been mechanically reduced. They do not immediately dissolve when scattered. They normally cannot be disbursed and blown away when scattered; so be mindful of that.
Second, while it is permissible in most states to scatter cremated remains, there are indirect legal requirements. No state law allow cremated remains to be scattered on private property without the consent of the property owner. (Common sense really dictates here though; what can you do on private property without the consent of the property owner? …nothing that I know of.) Many national and state parks have permit requirements and, sometimes location limitations for the scattering of those remains.
All that said — there are no “cremains police” in any state to ensure proper etiquette, permits, or permission are obtained and used. There are no health, safety or environmental issues to be concerned about and as such your own moral compass/judgment can be your guide to effectively do whatever you want within the reasons of common sense.
It’s a good practice to get the permission of the landowner to do anything on private land and when it comes to non-specific public land, don’t ask, don’t tell is as fitting advice as any. No laws say “yes” and no laws say “no.” Be advised that cremated remains can be stark white, a little like aquarium gravel, and therefore rather conspicuous, not at all like the “ashes from a campfire or fireplace”. So you may wish to consider a shallow burial unless you’re scattering in water. It is also highly advisable to use the road (or area) less traveled for the scattering ceremony; cremation and/or scattering is offensive to many people and cultures.
Within all the literary writings at all levels; federal, state, and local legislation – the only commonality agreed point of principle I have found is that the container which carries the remains must be disposed of separately – preferably is a waste receptacle.
It’s useful to mention that while most people searching for scattering advice tend to search regionally looking for State-based information… cremation (thus scattering) is not a state matter. You will mostly (if at all) only find information regarding State run or National Parks which can confuse your information findings. Most often you should be reviewing the local city or town ordinance and bylaws where the scattering ceremony is likely to take place.
Sacred Universe attempts to be as legally accurate as it can be for advice in every state and city. In fact, because scattering of ashes isn’t usually a state matter (with the exceptions of state parks and lands) we have included State Park Memorialization articles in the cremation chapter for your region which may contain additional information. City or town ordinance and bylaws will supercede these chapters “if available” and if not, most any public lands will normally align to the guidelines of the State park in your region.