Where am I allowed to scatter ashes?

If you're discreet and careful, you can scatter small amounts or the whole four pounds of bone byproduct safely and respectfully many meaningful places, but please think this out and take care. You may deposit cremated remains of a pet or a human in the soil of a forest, lake or ocean. National parks are fairly tolerant, but call ahead and get the rules. For out-of-town scatterings, the certificate given to you by the crematory and a note from your funeral director should accompany the cremated remains when hand-carried on airplanes. 

For ocean scatterings, the U.S. Coast Guard requests three nautical miles off coast. Try not to get arrested like the man from Dallas visiting New York City who sprinkled a friend’s remains in the orchestra pit of the Metropolitan Opera House. Though he was soon released, the show concluded that day at intermission! And evening performances were cancelled as well. Folks feared the powder was anthrax.

https://www.nytimes.com/2016/11/03/arts/music/opera-fan-apologizes-for-scattering-ashes-at-metropolitan-opera.html