Officials in Oregon and Democratic-led cities across the country will be closely watching a key court hearing Thursday over whether President Donald Trump has the legal authority to deploy the National Guard to Portland .

No matter the outcome, Trump may hold the trump card.

If the 9th U.S. Circuit Court of Appeals upholds a federal judge’s ruling that temporarily bars Trump’s attempt, Trump has another tool he could use for sending the military to the streets of the entire city — let alone guarding the U.S. Immigration and Customs Enforcement facility in South Portland.

It’s a little understood, more than two-century-old law: The Insurrection Act. First passed by Congress in 1792 but significantly added to in subsequent years, it’s often referred to as the Insurrection Act of 1

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