The US Park Police quickly moved tourists out of the way and sectioned off the area with yellow police tape. After three warnings, the police started to arrest participants one by one.

Among those placed under arrest was Gus Speth, former chair of the US Council on Environmental Quality under President Carter and co-founder of the environmental group Natural Resources Defense Council.

In an interview with Dow Jones, Speth said the pipeline would be used to transport a type of crude oil -- known as tar-sands oil -- that would encourage a continued reliance on fossil fuels and emit harmful pollution into the air.

We have lost our voice in this USA administration.