Six days after Sept. 11, 2001, as New York City reeled from the worst terrorist attacks on United States soil, lawmakers in Albany passed sweeping antiterrorism laws. Since then, prosecutors have used them infrequently.

But last week, the Manhattan district attorney’s office leveled a terrorism charge against Luigi Mangione, a 26-year-old man accused of killing a health insurance executive, classifying the crime not just as a murder but also as an attack on democracy.

Prosecutors’ decision to characterize the killing of the UnitedHealthcare chief executive, Brian Thompson, as a political act will test the law. And it will have implications beyond the courtroom.

The defendant, who carried a handwritten manifesto decrying the American health care system, has been cast as a martyr by some people sympathetic to his apparent philosophy — and the charges could strengthen that perception. Some have criticized what they see as a judgment by the authorities that the killing of a wealthy executive is more important than the deaths of the anonymous poor. And as a practical matter, terrorism could be a more difficult charge to prove than second-degree murder.

Alvin L. Bragg, the Manhattan district attorney, has argued that the terrorism charge is warranted because the gunman’s action was meant to do more than kill Mr. Thompson — it was meant to send a message to the public. Mr. Mangione, he said at a news conference last week, intended to “sow fear.”

“This type of premeditated, targeted gun violence cannot and will not be tolerated,” Mr. Bragg said.