British tourist Michael Sandford's starting a jail term of one year and one day for causing a scare at a Donald Trump rally in Las Vegas in June.
Sandford tried to grab a police officer's gun at the event.
It wasn't clear in court whether he intended to harm Trump, then the presumptive Republican presidential nominee.
Sandford, who'd overstayed his visa by ten months at the time of the incident, admitted illegal weapons possession and disrupting the orderly conduct of the rally.
Sandford's mother told reporters in August he'd been diagnosed with a series of mental health disorders and was on suicide watch in jail.
A Justice Department statement said the sentence reflected the scale of the response needed to the threat he posed and his arrest had disrupted Trump's speech.