The pair, who already have a checkered disciplinary record, posed for the pictures at a gun shop in the United States where members of the Australian Olympic swimming team had been training and competing in the lead-in to London.
The 24-year-old swimmers apologised after being slammed by anti-gun groups in Australia and stripped the photos from their accounts under pressure from governing body Swimming Australia.
"The Australian Olympic Committee (AOC) has decided Nick D'Arcy and Kenrick Monk will be sent home to Australia at the conclusion of their swimming events at the 2012 London Olympic Games," the AOC said in a statement on Saturday.
"The AOC Selection Committee met today and also decided that D'Arcy and Monk will be banned from using social media, including Twitter, Facebook and blogging, for the Games' period of July 16 to August 15, 2012.
Australia chef de mission Nick Green said he had concerns regarding the swimmers' "lack of judgement" in a letter to the pair.
"Australian Olympians are required to meet very high standards of conduct and we cannot risk the reputation of the team," he said in an excerpt carried by the AOC statement.
The pair's inclusion on the Australian swim team had already been contentious.
D'Arcy was kicked off the 2008 Australian Olympic team after punching former swimmer Simon Cowley at a bar, causing severe facial injuries.
D'Arcy was later ordered by a court to pay Cowley damages, but avoided payment by declaring bankruptcy.
Monk last year told police he was the victim of a hit and run accident only to confess later that he had suffered his injuries, including a broken arm, when he fell off his skateboard.
Green said the decision to allow them to compete had nothing to do with their medal chances.
Monk qualified for the Games in the 200 metres freestyle, while D'Arcy booked his ticket in the 200 butterfly.
"This has nothing to do with medals; it is all about upholding team values, in particular the high standards of behaviour set by those Olympians who came before you," he said.
The AOC said the punishment was separate to a disciplinary process being carried out by Swimming Australia (SA).
SA said they supported the AOC's decision, adding that they had yet to finish their own internal process and would meet with the swimmers on Monday.
"We will be speaking with the athletes involved further about this matter, and reminding them about their responsibilities as representatives of the Australian swim team," SA said in a statement on Saturday.