Note to The Merchant of Venice, 4.1.39. "Upon your charter and your city's freedom"
Upon your charter and your city's freedom: —Venice was a great trading city, and its citizens did business with a multitude of foreigners. Its "charter" would state the rights, privileges, and restrictions of merchants doing business in the city. Its "freedom" would be laws granting freedom to foreign merchants to conduct business on the same terms (or nearly so) as Venetians. Shylock's threat is that if his contract with Antonio is not enforced by the Duke of Venice, every merchant in the city would doubt whether or not the rules of the charter and the freedoms would be enforced. Shylock implies that if his contract with Antonio is not enforced, all merchants would doubt whether any contract would be enforced, and business would grind to halt.