The Keystone XL pipeline, the $5.4 billion project that would directly connect Canada's oil supply to the US' Gulf Coast, could face future delays following a ruling by a Nebraska judge. In an order today, US District Court Judge Stephanie Stacy said that last January's approval by Nebraska Governer Dave Heineman to go ahead with the project violated the state's constitution. As a result, Judge Stacy says the decision is now null and void, The Washington Post reports.

That's bad news for the controversial project, which aims to build a 1,179 mile long pipeline from Alberta, Canada all the way to Nebraska in the US. Last month the State Department released the final results of its environmental analysis on the project, where it raised no major objections. Still needed is a go-ahead from US President Barack Obama, who rejected an application of the pipeline two years ago over environmental concerns. That's caused tensions between the US and Canada, which stand to gain in the export of some 830,000 barrels of oil each day.

Nebraska's Attorney General Jon Bruning already said he's appealing Stacy's ruling, something that could reverse the decision.

The Keystone XL project has attracted controversy since it was proposed in 2008, primarily for its potential environmental impact. Earlier iterations or the pipeline garnered extra scrutiny by the Environmental Protection Agency, which voiced concerns over the possibility of heightened greenhouse gas emissions and accidental spills. Proponents of the project have argued that it will create new jobs, and strengthen North American oil production.