First, finding useful things to do with all those military people outside of wartime is a major issue especially when they need to suddenly stop doing that during a war. Second, a lot of civil infrastructure has military implications. EX: It's hard to make a dam you can't take out with explosives, but you can do a lot of things down stream to make destroying it less important.

So, as a bonus it keeps the organization's skills up to date.

The land was illegally annexed by the government. The Sioux signed a treaty that was broken by the US, were offered money in compensation for the land, which they refused. That land abuts the reservation's surface water sources. Without it they have no water security, an asset they consider priceless.

The ownership remains contentious.

That land was stolen from the Arikara/Sahnish by the Sioux using guns and horses acquired from trading with Europeans. The descendants of the Arikara/Sahnish now live on the Fort Berthold Indian Reservation.

The venue to resolve this dispute was in the courts and the timevto do it was Years and decades before there was a project planned for that land. However, if we're really going to go down this absurd path, let's take the entire Standing Rock reservation away from the Sioux and hand it over to the Arikara/Sahnish.

I just want to emphasize that I made no assertions about the true "rightful owner of the land." I don't think there'd be a problem if the army wanted to build a wind farm or solar farm, or even housing on the land. They want to build an oil pipeline. The problem with framing this as a ownership dispute is that that is a overly reductive minimization of the actual issue: water security.

The city of Bismarck to the North asserted its political right to water security over land it didn't own when it forced the pipeline to reroute South, to the current planned route over the reservation.[0] Now, the Native Americans are being forced to take the risk that the 95% white city community found unpalatable.

0. http://www.huffingtonpost.com/entry/a-nodapl-map_us_581a0623...

Shouldn't the USA honor its treaty obligations?

The US didn't break the treaty first (or even second). The truth is that there isn't clear pedigree to that land near as I can tell. I've tried to figure out title as far back as 2004. Beyond that, I'd probably have to go to Morton County to figure out more. It's very likely that if you go back far enough, it was transferred under the Dawes Act. Whatever the pedigree, the venue to deal with this dispute was in the courts well before 2014. The courts are the right venue to determine who owns the land, not the court of public opinion. The entire conflict happening there is an exercise in virtue signaling by environmentalists that are using another cause to further theirs. It's populism and vigilantism rolled into one. Institutions like the US Justice system actually work really well by global standards. Allowing disputes to negotiated outside the court system adds lots of legal uncertainty that destabilizes day to day life.

FWIW I wasn't even born in the United States, but I am an immigrant that has been here since 1986.

I find that history interesting.

What absurd path? I honestly don't understand what you are getting at.

The absurd path of the court of public opinion and a cultural marxist framed discussion of the "oppressed vs oppressors". Protesting on land that is currently recognized as private land is depriving its owners of its use. If the ownership is in dispute, the venue to resolve that dispute is in the courts. Literally no one cared about the land until a pipeline was going to be placed on it.

FWIW, my original source for this information is a friend who is 1/4 Sioux and thinks the protest is absurd. I've fact checked his claim. The Sioux only occupied the land east of the Missouri river in pre-contact America. The Arikara/Sahnish were agrarian people driven off their land by the Sioux.

The problem with going to court is precedent. The Sioux don't want the court to rule in favor of the government. That would set precedent about the government's ability to force the exchange of native land for fiat currency.

The problem is that in the west private ownership carries with it a right to destroy. If the army corps wanted to build a wind farm on the plot, there wouldn't be a problem. They want to build an oil pipeline over the water supply.

If a disaster were to occur, there is court precedent for abdicating the company of any responsibility for cleanup.[0] The present administration's Indian Affairs appointee wants to preserve this privatization agenda at all costs[1], so there's even less likely recourse if damages should occur.

0. http://articles.timesofindia.indiatimes.com/2012-06-28/india...

1. http://www.reuters.com/article/us-usa-trump-tribes-insight-i...

Not the op, but I think they mean by "absurb path" that if the land is taken from the Sioux and given back to the Arikara/Sahnish because the Sioux took it violently, there might be quite a lot of other US land that has to be given back as that too was taken violently.