The Supreme Court's ruling brings to an end a number of judicial reviews on the first stage of the project, brought against the Government by environmental campaigners, local authorities and residents from areas that the HS2 line will pass through. It confirms previous rulings by the High Court and Court of Appeal, after the Department for Transport (DfT) took action to rectify the one challenge upheld by the former in March 2013.
Infrastructure law expert Patrick Twist of Pinsent Masons, the law firm behind Out-Law.com, said that with the legal challenges out of the way the Government could now concentrate on its "ambitious" plans to obtain Royal Assent for the HS2 Hybrid Bill before the next election.
"The DfT and HS2 Ltd will feel that this outcome supports the way that the project has been promoted," he said. "Of 10 judicial reviews sought, only one, concerning limited aspects of the consultation process, was granted. The Government has taken this on board and has revised the consultation."
"The debate now moves away from any legal challenge and exclusively into the parliamentary and political arena. The next crucial event will be the second reading of the Hybrid Bill: the Government had originally intended this to take place in early April but Parliament has recently extended the deadline for commenting on the Environmental Statement with the result that Second Reading will not now take place until the end of April at the very earliest," he said.
Earlier this week, a House of Lords committee extended the deadline for responses to the consultation on the potential environmental impact on the scheme by a further two weeks, following a similar ruling by MPs in the House of Commons. The consultation will now close on 27 February 2014.
The DfT has said previously that it intends for the Hybrid Bill, which it has described as the "planning application" for HS2, to achieve Royal Assent by the end of the current Parliament in 2015, allowing construction of Phase One to begin in 2016 or 2017. This initial London to Birmingham section of the route is currently scheduled for completion in 2026, with a proposed second phase connecting the line to Manchester and Leeds envisaged by 2033. This second phase will require separate planning, consultation and legislation.
The Supreme Court ruled on a number of challenges relating to the application of two EU environmental directives. Protest groups HS2 Action Alliance, supported by the '51m' group of local authorities affected by the scheme and Heathrow Hub, claimed that the Government was required to comply with the Strategic Environmental Assessment Directive and failed to do so. The local authorities also claimed that the Hybrid Bill would breach the Environmental Impact Assessment Directive.
The seven judges concluded that these claims either did not apply, or were based on an "incorrect interpretation" of the relevant directives. They also ruled that there was no justification for referring the case to the Court of Justice of the European Union (CJEU).
"There is ... no reason to suppose that Members of Parliament will be unable properly to examine and debate the proposed project," said Lord Reed.
"Without therefore considering the fundamental constitutional objection to this line of argument - that the court would be presuming to evaluate the quality of Parliament's consideration of the relevant issues, during the legislative process leading up to the enactment of a statute - I conclude that the argument is based on an incorrect interpretation of the EIA Directive, and is in addition unsupported by the evidence as to the procedure which might be followed," he said.
The Government welcomed the Supreme Court's "unanimous" rejection of an appeal that "addressed technical issues that had no bearing on the need for a new north-south railway".
"We will now continue to press ahead with the delivery of HS2," said Transport Minister Baroness Kramer. "The new north-south line will provide extra space for more trains and more passengers to travel on the network, delivering additional capacity where it is most needed. HS2 will also generate thousands of jobs across the UK and provide opportunities to boost skills."