When Canadian Prime Minister Justin Trudeau was sworn into office Wednesday, he ushered in a new era of pipeline politics that places the future of three major projects in question: Enbridge’s Northern Gateway pipeline, Kinder Morgan’s Trans Mountain pipeline and TransCanada’s Energy East line.

Collectively, these projects span 4,200 miles and aim to ship more than two million barrels per day of Alberta’s landlocked tar sands oil to the Atlantic and Pacific coasts for refining and export. Trudeau has promised to cancel Northern Gateway, but indicated more support for Trans Mountain and Energy East (as well as the long-delayed Keystone XL, whose fate is doubtful because of U.S. opposition).

Nonetheless, Trudeau and his Liberal Party have pledged to revamp the National Energy Board’s pipeline review process by increasing environmental scrutiny for proposed projects.

Reforming the NEB will likely delay ongoing pipeline reviews. Legal challenges will add other obstacles.

Trudeau’s administration replaces the Conservative Party government led by Stephen Harper, who supported the oil sands industry during his nearly 10 years in office. (Trudeau is the son of the late Pierre Trudeau, a former prime minister who led the country from 1968-1979 and 1980-1984).

The Liberal Party’s more climate-friendly stance, along with a steep drop in crude oil prices and sustained anti-pipeline activism, has energized green groups.

Adam Scott, climate and energy program manager at Environmental Defence Canada, believes current economic and political factors will hinder the tar sands industry’s growth.

On Thursday, hundreds of climate activists will stage a sit-in at Trudeau’s residence in Ottawa. They will urge him to take a stronger stance on climate issues and demand an end to tar sands expansion.

Here’s a summary of the three pipelines’ current status:

Enbridge’s Northern Gateway

The former Conservative government granted a conditional approval last summer, pending a slew of requirements on the pipeline’s environmental protections and consultations with First Nations. Environmental groups and aboriginal communities challenged the approval in court, and a decision is pending from a Canadian Federal Appeals Court.

The pipeline, which would bring 525,000 barrels of tar sands oil per day from Alberta to the northern British Columbia Coast, has faced years of opposition from First Nations. Because many First Nations in British Columbia never signed treaties with the Canadian government, they hold strong legal rights that pose a formidable challenge to pipeline construction. Scott said the extent of that power is being tested in court.

Trudeau’s clear stance against Northern Gateway prompted the Vancouver Sun to declare the project was “likely dead” shortly after Trudeau’s party won the election last month.

The Liberal Party did not respond to requests for comment. 

Enbridge spokesperson Cory Paterson said in an email that the company shares “the vision of the Trudeau Government that energy projects must incorporate world-leading environmental standards and First Nations and Métis ownership…The project proponents remain committed to Northern Gateway and building this important Canadian infrastructure.”

Kinder Morgan’s Trans Mountain Pipeline Expansion

The existing Trans Mountain pipeline carries up to 300,000 barrels of oil per day from Alberta to the southern British Columbia coast. Kinder Morgan’s expansion would add a new parallel pipeline to increase oil flow to 890,000 barrels per day.

First proposed in 2013, the project is under NEB review. The Tsleil-Waututh Nation filed a lawsuit last week in federal court challenging the NEB’s authority and its “deeply flawed” process.

“Governments have a legal obligation to consult with First Nations. But the NEB’s review was designed without First Nations consultation or public participation, ignoring the duty to consult and accommodate on decisions affecting Aboriginal rights set down by the Supreme Court,” Tsleil-Waututh Nation Chief Maureen Thomas said in a statement.

This case “presents an opportunity for the new Liberal government to affirm its commitment to fixing the flawed regulatory system for pipelines,” the statement said.

The NEB did not respond to a request for comment.

TransCanada’s Energy East Pipeline

This 2,858-mile pipeline is the largest of the three proposed projects, with a capacity of 1.1 million barrels a day. About 1,000 miles of the pipeline would be built from scratch, while the rest will be repurposed from an existing natural gas pipeline. TransCanada will also build new pump stations, at least one marine terminal and connections to link the pipeline to three refineries in Quebec and New Brunswick.

TransCanada submitted its initial application to the NEB in October 2014. Last April, the company withdrew its plans to build an oil terminal in Cacouna, Quebec, due to concerns that construction would harm endangered beluga whales. Another terminal, in Saint John, New Brunswick, is still slated to be built.

On Nov 5, TransCanada announced it would cancel the Cacouna terminal and stick with the single terminal at Saint John.

Company spokesman Tim Duboyce said the company will file its remaining documents to the NEB by the end of 2015, and he expects NEB hearings to begin next year. If approved, he said, the pipeline would be in service in 2020.

He said he doesn’t anticipate delays from Trudeau’s pledge to reform the NEB. “We look forward to working with the new government,” Duboyce said.

Update 11/6/15: This story has been updated to reflect TransCanada’s plans for the Cacouna terminal.