A walkway connecting a pair of heritage buildings near Parliament Hill will be walled off to avert a constitutional crisis involving Canada's highest court.

The walkway, known as the Memorial Colonnade, is an arch or bridge above Lyon Street that allows federal employees to walk comfortably between the buildings — out of the rain, wind, humidity and snow of Ottawa's changing seasons.

The East Memorial and West Memorial buildings, each facing Wellington Street, were constructed between 1949 and 1962 to house the rapidly expanding Veterans Affairs Department. The arch commemorates those who served in the Second World War.

The Memorial Colonnade, which people use to go between two buildings, will be sealed off when the Supreme Court of Canada moves into the West Memorial Building. (CBC)

Today, the East Memorial Building is home to the federal Justice Department, including the office of the justice minister and attorney general of Canada.

The West Memorial Building has been vacant since 2008, and costs about $1.7 million for operations and maintenance each year.

But the west building is getting an important new tenant: The Supreme Court of Canada, including the offices of the nine justices, some 280 staff and three high-ceilinged courtrooms.

The big move is set to be complete by 2023, so the crumbling main Supreme Court building on Wellington, completed in 1940, can get a long-overdue, five-year makeover.

$1B rehabilitation project

The entire undertaking — fit up of the West Memorial Building, move, rehabilitation of the main Supreme Court building, and move back — is expected to cost taxpayers $1 billion.

But the whole project is contingent on erecting a simple, relatively inexpensive wall to block that pedestrian walkway.

That's because Canada's form of constitutional democracy requires a clear separation of its three branches; that is, Parliament, the government and the courts.

This is to ensure the conceptual and operational independence of the Supreme Court of Canada. - Public Services spokesperson

And a physical walkway between the justice minister's offices and the high court would offend that fundamental principle of separation, both practically and symbolically.

The wall "is to ensure the physical separation of the Supreme Court of Canada in the West Memorial Building from the federal judicial functions within the East Memorial Building," said Jean-François Létourneau, a spokesperson for Public Services and Procurement Canada, which is responsible for federal real estate.

"This is to ensure the conceptual and operational independence of the Supreme Court of Canada is maintained during their interim occupancy."

A second wall is also planned to seal off an underground pedestrian tunnel that also connects the two buildings.

"The Colonnade and tunnels will be reopened once the Supreme Court of Canada moves back into the rehabilitated Supreme Court of Canada building," said Nicolas Boucher, another Public Services spokesperson.

The walls — known as demising partitions — will be built sometime between 2019 and 2023, as the West Memorial Building is rehabilitated.

A Public Services spokesperson says the wall "solution" was developed by the department rather than the high court.

Court guards independence

The Supreme Court of Canada jealously guards its independence from government, and last year won its most recent skirmish.

In 2015, the Harper government issued an order requiring federal departments — including the Courts Administration Service and the Registrar of the Supreme Court of Canada — to obtain their IT services, such as data storage on central servers, from Shared Services Canada by Sept. 1 of that year.

The high court dug in its heels, refusing to comply and threatening action — all in defence of its independence from government.

The justices' objection had a practical side: about a third of the cases that come before the high court are brought by the federal government, so confidentiality on each side is necessary to ensure the integrity of the judicial process.

Data from both sides cannot be kept on the same server, the court argued.

In the end, the Liberal government altered the cabinet order on Jan. 13, 2016, no longer requiring the court to use Shared Services Canada. The Supreme Court now maintains its data on servers independent of government, though it does use Shared Services Canada to acquire secure hardware.

Electrical and other systems are at serious risk of failure in the existing Supreme Court of Canada building, which is getting a $1-billion makeover. (CBC) In the meantime, the high court faces a serious challenge to keep its current offices running in a building that's almost 80 years old.

Internal documents from Public Services and Procurement Canada, obtained by CBC News under the Access to Information Act, show several systems are expected to fail before the move to the West Memorial Building by 2023.

"Several building components are well beyond the expected life cycle and at significant risks of failure," warns one document from July of last year. Faulty systems include old wiring, leaky radiators and substandard plumbing.

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