Alberta is threatening to use its supply of petroleum products as a "weapon to change the politics of British Columbia," lawyers for B.C. argued in a Calgary courtroom Friday.

Legal counsel for B.C.'s attorney general was in court seeking an injunction with plans to challenge Alberta's brand new Bill 12 as unconstitutional.

"There is a loaded gun and we need to make sure that it doesn't accidentally go off," Gareth Morley told Court of Queen's Bench Justice Robert Hall.

Bill 12 gives Alberta the power to cut off oil and gas exports to other provinces. It was originally passed under Alberta's previous NDP government as leverage in talks with B.C. Premier John Horgan over his government's opposition to the Trans Mountain pipeline expansion project. It then was proclaimed into law on April 30 at the first cabinet meeting by the newly elected United Conservative Party government under Jason Kenney.

Within hours of proclaiming the legislation, lawyers for B.C. filed an injunction application and constitutional challenge in an attempt to block the new law.

Hall must decide two issues: whether B.C. has standing in Alberta court to make its application and, if it does, the judge must decide if he'll grant the injunction. Before reserving his decision, Hall expressed concern about the law, saying "there's a very serious danger of it being used" in the meantime. No return date has been set.

Purpose of law to 'cause pain'

Earlier in the day, the Alberta government argued its neighbours do not have standing to make their application in Alberta's courts.

Alberta's lawyer, Evan Dixon, told Court of Queen's Bench Justice Robert Hall that, if he allows B.C. to make its application, the judge would be opening the doors to the potential of a "floodgate of new litigation."

"Attorneys general from all over Canada could march into courts in other provinces challenging legislation that they don't like," said Dixon.

Gareth Morley, B.C.'s lawyer, agreed the case is unprecedented — but, he said, so too is the circumstance.

"In the whole history of this country, no province … has ever enacted legislation where the minister introduces a government bill and told the house that the purpose of that bill is to cause pain to the residents of another province," said Morley.

'Let's play fool-the-judge'

Kenney has insisted the new law is only to be used as a last resort if the B.C. government continues to do "everything it can to block the [Trans Mountain pipeline] expansion."

Still, Dixon argued that the B.C. government is "far removed from anyone that might actually be impacted by the act" which, he said, on its face is neutral and not aimed at targeting British Columbia.

The judge said press releases and comments made by UCP politicians make clear the intention of the law.

"It so clearly is aimed at B.C. that everyone calls it the 'turn-off-the-taps legislation,'" said Hall.

"I don't like to hear Alberta say to me, 'Oh, no, this isn't aimed at B.C.' when it clearly is: it's like you're saying 'let's play fool-the-judge.'"

If Hall grants the injunction, B.C. lawyers will argue the law is in violation of the Constitution because it restricts trade across provincial boundaries.

Bill 12 requires exporters to obtain licences and gives Alberta's energy minister the power to decide how much fuel is exported, the mode by which it's transported and whether direct shipments should be stopped altogether.

But Dixon has also argued B.C.'s injunction application is premature and shouldn't have been filed until the Alberta government made moves toward acting on the legislation.

The bill is also known as the Preserving Canada's Economic Prosperity Act and was originally passed under the previous NDP government but never enacted into law.

Earlier in June, the British Columbia government filed a second lawsuit in Federal Court in case it's found not to have standing in Alberta's superior court.