The U.S. Supreme Court’s renewed scrutiny of how federal law defines “regular forces” as it evaluates President Donald Trump’s attempt to send the National Guard to Chicago could shape the outcome of Oregon’s troop case , legal observers say.

Last week, the Supreme Court asked attorneys in the Illinois case to file additional briefs on how the court should interpret the phrase “regular forces” in federal statute’s Title 10, Sec. 12406, which Trump invoked to call state National Guard members into federal service.

The president may deploy National Guard members when he’s unable “with the regular forces” to execute the laws of the United States, the law says.

Lawyers have disagreed over whether “regular forces” refers to civilian law enforcement — such as Federal Protective Service or

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