This contribution explores the tension that existed in the nineteenth century in the Southern Netherlands between the liberal legislation and the principle that markets without official recognition were illegal. How did the authorities deal with that tension? The focus here is on ‘real’ markets: formal or informal gatherings of buyers and sellers for the purpose of trading commodities, often with a certain periodicity, sometimes in public, sometimes in private places. The first part goes through the restrictive rules on the establishment of such markets. The second part confronts these rules with the implications of the liberal decree d’Allarde, declaring the exercise of all professions free. Finally, the last part explores the legal means this ambiguous legal framework offered to act against illegal markets: markets being held without official recognition. This contribution shows that it mainly depended on local authorities whether such illegal markets could continue to exist.