The man placed the stone, which marked the border for more than 200 years, 2.29 meters in France after obstructing his tractor.
The slight change in boundary was noticed several weeks ago by an amateur historian during a walk in the forest.
The farmer “has also repositioned his fence on trees belonging to the wood of Bousignies”, according to Aurélie Welonek, the mayor of the French town of Bousignies-sur-Roc.
The stone was first laid there in 1819, before the 620 km (390 mile) border was officially established under the 1820 Treaty of Kortrijk.
David Lavaux, the mayor of the Belgian village of Erquelinnes, said the farmer will have to move the stone or could face criminal charges.
“We have no interest in expanding the city or the country. He enlarged Belgium and France smaller. It’s not a good idea, ”he told the French television channel. TF1.
He added: “I was happy, my city was bigger. But the mayor of Bousignies-sur-Roc did not agree.
” And [the farmer] shows good will, he will not have a problem, we will settle this issue amicably, ”Lavaux said with a smile.
If the terminal is not returned to its usual location, a Franco-Belgian commission could be set up to determine the exact border.
The last such commission took place over 90 years ago, according to Lavaux.