The Financial Post reports in its Saturday edition that Canadian energy producers and pipeline companies are preparing for U.S. President Donald Trump's proposed 10-per-cent tariff on energy. The Post's Meghan Potkins writes that there is, however, uncertainty about how the tariff will be calculated for cross-border oil and gas flows. Energy law lawyer Jason Fleischer says developing mitigation strategies is challenging. Historically, the sector has not faced such tariffs since the 1970s oil crisis. Unlike current customs duties of about five to 10 cents per barrel, the new tariff may vary based on the commodity's market value at the border, but specifics remain unclear from U.S. officials. The owner of oil or gas, typically the shipper, is responsible for paying tariffs on export pipelines, as per trade experts. Companies are reviewing contracts to clarify payment responsibilities. With Mr. Trump's March 4 deadline approaching, there is still uncertainty about whether Canadian energy that temporarily crosses into the U.S. would incur tariffs. For instance, crude from Alberta travels through the U.S. via Enbridge's pipelines before returning to Canada, and some Canadian oil goes to the Gulf Coast for re-export.