Companies will not be issued with licenses to import electricity from the Astravyets plant once it is launched.
Moreover, if a governmental commission vetting deals by strategic enterprises decides that an importer poses a national security threat, its license will be suspended.
The Seimas passed on Thursday the respective legislative amendments, tabled by President Gitanas Nauseda, in a vote of 105 to none with nine abstentions.
The amendments should take effect in January 2020.
In 2017, the Lithuanian parliament passed a law declaring the Astravyets plant a threat to national security, environment and public health.
It has also adopted a law banning electricity imports from unsafe plants.
The government says the Astravyets plant under construction some 50 kilometers from Vilnius fails to meet international safety standards, an allegation that Minsk denies.