The answer of course "it is legal with local ordinances observed - see information below". However, if you're really wanting a special experience and in the Colorado area I've always thought the most amazing place to pay back the earth with a loved ones ashes would be at the top of Pikes Peak. It's history is rich in our nation, but more importantly the view will be one of the most memorable for each family and friend involved. Keep and eye out on the weather and choose a day when the sun is at your back, and the winds will carry the ashes far. I can't think of a more fitting place to pay back a life well lived. As far as a party afterwards, those ashes will be carried to places near and far getting the most coverage. That's a celebration in itself. You could make a day/evening of remembrance by creating your own "wake" or if there is Indian heritage it would be fitting to observe any ancient rites, and or ceremonies fitting to the specific tribe. These are suggestions, and will be a unique time of reflection and acceptance for all. The good news is there are no noted regulations "inland", there are however rules if you choose to include a water body.
*See information below:
Scattering Ashes / Laws & Regulations
Scattering ashes is an act of memorialization and isn’t a normal state matter (outside of State controlled parks and lands). This makes it difficult to find an appropriate answer.
If your scattering ashes ceremony is to be held within a city or town limits this suggests that city/town ordiance and bylaws should be consulted.
more here: http://www.cremationsolutions.com/Scattering-Ashes...
Funeral Customs — Native American
Native American Funeral Services http://www.funeralwise.com/customs/native_american