The hundreds of thousands of US federal employees furloughed by Congress' failure to appropriate funds for the 2014 fiscal year are legally required to turn off their work phones. If they check their work email they can be fired and may face civil or criminal penalties.

Government shutdown procedures vary by agency. Some, like the Committee on House Administration told non-essential personnel that it "strongly recommend that you turn your BlackBerrys off for the duration of the furlough," while others mandate employees to hand in their work-provided cellphones, reports Politico.

"We strongly recommend that you turn your BlackBerrys off for the duration of the furlough."

Why are agencies so strict about making sure furloughed employees don't do any work during the government shutdown? It all goes back to an obscure law passed in 1884 called the Antideficiency Act. The statute prohibits the government from agreeing to financial commitments using money that it doesn't have. It also bars the US government from accepting voluntary services. The law was originally designed to stop the executive branch from reaching around Congress by making financial contracts without specific approval from the legislature — effectively forcing senators and representatives to provide funds at risk of reneging on agreements.

Thankfully the Antideficiency Act provides for the government to accept volunteer services in emergencies that "imminently threaten the safety of human life or the protection of property." Those staff involved in "essential functions" are allowed to work with the promise of future pay once Congress passes an appropriations bill. The Atlantic has much more on the intricacies of the act, but it all leaves one intriguing problem: how do agencies tell furloughed employees when to go back to work? As the White House Office of Management and Budget warns, employees "should not rely on mobile devices or home access to work email for providing notices of when to return to work." It's likely they'll instead need to keep an eye on the news; or wait for a personal phone call, email, or, possibly, a tweet or Facebook update.