Took images of Native Americans at public invited Powwow. Do I need model releases?

I took some nice photos of the participants while they were dancing. I am under the impression that images of people in a public outing or festival do not need model releases.

By @Michael Ohl

What makes you think that?

First they have the right to control their own public image. That is not diminished by the fact that they were performing on a public event. 

Second, they may have performed in some setting, that by itself is protected by intellectual property. You simply can't go and take pictures and publish those pictures, when may be part of their living is made by selling photos of their performance to interested parties. The buyer would maybe prefer to buy from you, even that you were in nothing involved in the hard work prepareing the performance. 

Third, publishing something on Adobe stock makes that generally available, and anyone could buy a licence and publish a billboard advert with their performance, even if they do not identify with that product. 

So, that's why all stock plattforms require an unconditional model release. 

Fourth the organizer of the venue may also have some rights to the performance, so you may also need their authorization.

If taking pictures were allowed (many venues also disallow photographing), those photographs are for your personal use only. 

Newspapers have different rules for newsworthy events, and even those won't publish any person as is withoput a proper consent. Therefore you sometimes see pictures or videos, where part of the video is blurred.

Adobe is not accepting assets for editorial use, if people are represented.