President Obama announced over the weekend that the construction of the Keystone XL Tar Sands Oil Pipeline was not in the national interests of the United States.

The decision culminates a seven year review process undertaken by the Department of State and throws into general doubt the export of tar sands oil to foreign markets.

Obama cited the following reasons for rejecting Keystone:

1. It would not make a meaningful long-term contribution to the U.S. economy
2. It would not lower fuel prices for American motorists (which have been dropping steadily along with the fall in crude oil prices)
3. Shipping the comparatively dirtier tar sands crude into the United States would not increase the country's energy security
4. The United States has to lead the global fight against climate change by example

Keystone XL would have linked existing pipeline networks in Canada and the United States to bring crude from Alberta and North Dakota to refineries in Illinois and, eventually, the Gulf of Mexico coast.

TransCanada, the pipeline project's main proponent, first sought the required presidential permit for the cross-border section in 2008 but the proposal provoked a wave of environmental activism that turned Keystone XL into a rallying cry to fight climate change. Blocking Keystone became a litmus test of the green movement's ability to hinder fossil fuel extraction in Canada's oil sands.