The Keystone Pipeline System has transported oil from Alberta, Canada, to the US states of Illinois and Texas since 2010, but a proposed expansion, Keystone XL, has been a sticky subject for the two countries.
In 2015, the fourth phase of the pipeline, which would run from Alberta to Nebraska, was vetoed by President Obama based on its environmental impact, but the project was then granted the go-ahead by his successor Donald Trump in 2019. Protests against the expansion continued and it wasn't long before it ran aground yet again.
President Biden revoked the permit just hours after his inauguration on January 20, 2021, again on the basis of the proposed expansion’s environmental impact. In response, Alberta Premier Jason Kenney said that the move would put people out of work and weaken the US-Canada relationship. The project was set to cost around $8 billion, which would have been privately funded.