Magistrates in Montpellier handed the 16 protestors, all members of France's activist agriculture union 'Confederation Paysanne', a €3,000 fine for their attack on Lactalis, France's largest dairy producer.
State prosecutors had called for an eight-month prison sentence for the leader, Jean-Emile Sanchez.
Tension between milk producers and processors in France has risen as farmgate milk prices have continued to fall, reflecting a Europe-wide trend.
Average milk prices paid to French producers have fallen €0.5 over the last five years, the biggest drop across the 15 pre-accession European Union nations.
It was in 2004 that Sanchez and other protestors broke into Lactalis' factory near Rodez. They quickly piled cartons of milk and packs of cheese into sacks before redistributing the products, worth a combined €2,000, to people in the local area.
The 16 claimed their action was retribution for the losses milk producers had endured over the previous four years.
Sanchez, speaking in Montpellier on Tuesday, criticised the French government for pursuing a prison sentence in the case, and said he and others would continue to fight an agriculture policy that had led to farmgate price cuts for all products.
"If the government wants to declare war on farmers, we will rise to the challenge and we will continue to victory," he told a crowd of supporters outside the court.
Luc Morelon, spokesperson for Lactalis, said the group was aware of the ruling in Montpellier but declined to comment.
Lactalis and its French dairy rivals, including Danone and Sodiaal, have already faced down renewed protests over milk prices during the last year. An industry-wide deal was struck in January to introduce a recommended national milk price, but rows have continued with both Lactalis and Sodiaal breaking the agreement this spring.
Lactalis reversed its price cut last week, saying it wanted to respect the national recommendations. The firm then joined the fierce criticism directed at rival Sodiaal.
"In some parts of southern France the price difference between us and Sodiaal is as much as €7, which is quite unacceptable," Morelon told DairyReporter.com.
"We think the national agreement is a good thing for farmers and companies," he said, but warned "if Sodiaal doesn't come back to the agreement, we will be obliged to leave the agreement again".
Sodiaal paid producers an average €23.7 for 100kg of their milk in May, compared to €26 and €25 paid by Lactalis and Danone respectively, according to new figures from the UK's Milk Development Council.
There has been a steady decline in farmgate milk prices across the European Union over the last two years, prompting producer protests in several countries. The drop reflects rising cost pressures on processors, including rising retailer power and soaring packaging and energy prices.
Farmgate milk prices were still higher in France this May than in several other countries, and notably Britain, which has continued to languish at the bottom of Western Europe's milk price league table.