From Sunday, people in DC have to show proof of vaccination to enter restaurants and other indoor venues.
GOP Rep. Thomas Massie slammed the mandate on Friday, saying his "office will not comply."
We will get our food from Virginia or we will bring it to work," he tweeted.
Republican Rep. Thomas Massie pledged to bring his own lunch to work or order food from Virginia in a boycott of Washington, DC's new rule of needing vaccination proof to enter restaurants.
"My office will not comply," the Kentucky congressman tweeted on Friday. "We will not show papers. We will not order takeout from restaurants that require papers for dine-in. We will get our food from Virginia or we will bring it to work."
"Shame has befallen our nation's capital."
The order, which took effect on Sunday, requires people aged 12 and older show proof of vaccination to enter any restaurant, bar, nightclub, sports venue, or gym in the city.
Washington joined other major US cities - including New York, Boston, and Los Angeles - in implementing similar requirements to counter a dramatic increase in COVID-19 infections.
Massie has been critical of vaccine mandates in the past: Last August, he compared vaccine passports to that tattoos that Jewish prisoners were forced to have at Nazi concentration camps. He later deleted the tweet.
He was also widely slammed last month after posting a Christmas photo of his family posing with military-style rifles, just days after a deadly school shooting in Michigan.