The authorities say Libyan men and women between 18 and 45 must now seek security clearance before going abroad.
This means permits will be issued by the intelligence services.
Eastern Libya is in a clear state of insecurity, with militias and terrorists groups such as the Islamic State vying for control of the country.
Given the state of the country, divided in two, with a UN-backed goverment sitting in Tripoli and a military backed government in the East, many doubt the ban will have a significant impact.
"This isn't going to work," says Mohamed Eljarh, a non-resident fellow with the Atlantic Council. "People are coming to Libya to join terrorists groups, not the other way around. There's no logic behind this. Basically the reasoning the military governor has given is flawed. I think the real motives behind this ban is to appease the salafists who are in an alliance with the Libyan National army."
This ban comes after the Eastern authorities tried to impose a separate ban on women under 60 from travelling abroad without a male guardian.
But it was met with fierce opposition and the military authorities decided to backtrack on it.
"According to some civil society activists in Eastern Libya, the ban is mostly targeted at civil society organisations and intellectuals," explains Mattia Toaldo, a Libya expert with the European Council on Foreign Relations. "In a way, they want to control their movements and keep them in check."
Eastern Libya is under the control of strongmen commander Khalifa Hafter.
"These two bans come at a time when atmosphere in Eastern Libya has become increasingly repressive," says Mary Fitzgerald, an expert on Libya based in Dublin. " Civil society actors are under increasing pressure. Because you have a situation where you have military governors in different parts of Eastern Libya. The self-styled Libyan National army headed by Hafter really takes its cue from Egypt and sees Egypt under Sisi and the repressive regime he has implemented has a model to follow."
The rival governments are due to meet in Algiers in the coming weeks. But a date hasn't been chosen yet and no one knows who will attend the talks.
"The key in all of this are the external actors that have been involved in the past two years," explains Fitzgerald. "In particular those who have been backing Hafter with military and other support. Finding a solution is linked to wether those actors will be able to pressure Hafter to force him towards a power-sharing agreement."