Eco-warriors among civic politicians across Canada were sent a reminder Thursday that their weapons are limited: They have no power to block pipeline construction.

For the first time in its 55-year history, the National Energy Board (NEB) ordered a municipal government to stand aside from oil and natural gas project planning and preparations.

The order included a landmark ruling that local governments lack authority under the Canadian constitution to interfere with requirements or directions placed upon energy developments by the NEB as a federal agency.

The decision clarified the division of powers over a lineup of projects forming for approval to reshape the Canadian oil and gas delivery network. Plans such as Energy East — TransCanada Corp.’s proposal for partial conversion and extension of its gas Mainline to carry oil across Ontario, Quebec and New Brunswick — have aroused increasingly vigorous interventions by municipalities along their routes.

After simmering for months the issue boiled over into a constitutional duel in British Columbia, where five major pipeline projects for oil and liquefied natural gas (LNG) export schemes are in varying stages of the regulatory process.

The NEB ruling made an example of the City of Burnaby, a Vancouver satellite where a mayor who leads a left-wing local politics coalition is campaigning for re-election Nov. 15 on a platform of stopping Kinder Morgan Canada’s plan to triple capacity of its Trans Mountain Pipeline across BC and Alberta to 900,000 b/d.

With Mayor Derek Corrigan giving the orders, Burnaby bylaw enforcement officers prevented Trans Mountain from clearing brush, cutting trees and drilling bore holes on a small section of a local conservation area. The work carries out an engineering and environmental assessment of alternative routes required by the NEB.

Corrigan vowed to appeal the board’s decision to the law courts, but his promise was not regarded as a significant threat. BC courts earlier this fall refused to grant his Burnaby administration an injunction to stop Trans Mountain from obeying NEB orders.

The City of Vancouver — led by a political ally of Corrigan, former New Democratic Party provincial legislature member Gregor Robertson — also recently lost a lawsuit aimed at delaying or stopping the Trans Mountain project. Vancouver unsuccessfully sought a court order for the NEB to widen its review of the pipeline plan into a formal, complete assessment of effects on global greenhouse gas emissions that are liable to result from Alberta oilsands production — everywhere, from northern bitumen mines to Asian refineries where tankers filled by Trans Mountain are expected to voyage.

Running counter to U.S. practices, Canadian courts have a healthy regard for NEB decisions and tend to shy away from tampering with them, bowing to the energy agency’s expertise.

The NEB said its Burnaby ruling does not invalidate civic ordinances and that ordinarily pipelines are required to comply with local and provincial standards. Civic and provincial governments or politicians remain entitled to participate in NEB cases, as interveners or outright opponents able to ask the board to halt projects or put conditions on them such as special safety or environmental standards.

But longstanding doctrines of Canadian federalism — “federal paramountcy” and “inter-jurisdictional immunity,” which resemble basics of the division of powers in the United States — require local authorities to stand aside when their bylaws conflict with national jurisdiction, the board ruled.

The contested Trans Mountain route survey work cuts down fewer than 20 trees and disturbs a fraction of 1% of the Burnaby conservation area, according to evidence before the NEB. “Compensation is available if there is damage that cannot be remediated,” the board said.