Hanseatic League broke Bruges by walking out

The Hanseatic League was a confederation of merchant guilds and trading cities across Northern Europe with no monarch, standing army, treasury, or formal legal jurisdiction over the foreign ports its members traded through — London, Novgorod, Bergen, and Bruges among them. When a host city or ruler abused Hanseatic merchants with unauthorized taxes or broken privileges, the League had no court to sue in and no army to send; each individual merchant negotiating alone had essentially no leverage against a city that controlled the port he depended on.

In 1358 the city of Bruges, funding its share of the Hundred Years' War, imposed taxes on Hanseatic trade that violated the merchants' existing privileges there. A single merchant or even a single city's Hansa contingent complaining to Bruges's council had no real threat to back it up — Bruges could simply ignore isolated protests, and often had.

Ordered every merchant out of Flanders, relocated the post, and required certificates proving non-trade, making withdrawal a coordinated rule Bruges depended on.

Total withdrawal removed all Hanseatic trade, maximizing economic impact on Bruges.

Certificates made compliance checkable, preventing secret trade that would undermine the boycott.

Bruges depended on Hanseatic trade, so the loss caused real pain, forcing capitulation.

The League's control over the entire network made its threat credible, unlike individual merchants.

A voluntary network without legal or military power can enforce terms by making access to its collective business conditional, and threatening total, verified withdrawal.

Deprived of Hanseatic commerce, Flemish cloth production collapsed and the local economy suffered severe hardship; by 1360 Bruges had capitulated to the League's full demands and Hanseatic trading privileges there were restored.