The Morton County Sheriff's Department said on its Facebook page
that both Stein and her running mate, Ajamu Baraka, have been charged with criminal trespass and criminal mischief, both misdemeanors. The office also says it has video of the event.
Stein, who was not arrested at Tuesday's protest, admitted in a statement to spray-painting the bulldozer during the anti-oil demonstration, which concerned construction that she said amounted to desecrating Native American burial sites.
The bulldozer now has the phrase "I approve this message" emblazoned in red across its blade.
Footage of her shaking a can before painting her message onto the bulldozer at the site in St. Anthony could be seen in local media on Tuesday as well.
The company Energy Transfer Partners is behind the pipeline construction, though it is unclear who owns the bulldozer.
In her statement, Stein blasted North Dakota law enforcement and the Dakota Access pipeline, calling the spray-painting an act of "civil disobedience." She said the bulldozer she painted was one of several that "were used to assault the ancestral grave sites of the Standing Rock Sioux nation."
"I hope the North Dakota authorities press charges against the real vandalism taking place at the Standing Rock Sioux reservation: the bulldozing of sacred burial sites and the unleashing of vicious attack dogs," Stein said.
Stein was in North Dakota with dozens of demonstrators to protest the building of the Dakota Access Pipeline
, a nearly $4 billion effort to construct a pipeline linking the Bakken shale formation, a large shale oil deposit in the state, with oil refineries on the Gulf coast.
Displaying her activist credentials, Stein spoke to some of the protesters about the pipeline and did some campaigning as well. She described herself as "someone who's been here with you on the frontlines" and joined a scattered "Where's Obama?" chant.
Stein has a history of environmental activism, and during her presidential run in 2012, was arrested outside a debate to which she was not invited.