What is the ruling on evading the payment of rent for vendor stalls in European markets, based on the claim that it is permissible to appropriate the property of a non-believer in a non-Muslim country? And are these practices considered a form of permissible appropriation of wealth, similar to the story of seizing Abu Sufyan's caravan?

Allah Almighty says: {And fulfill [every] commitment. Indeed, the commitment will be questioned.} Stealing the wealth of disbelievers who have a covenant or are granted security is forbidden, with no disagreement among scholars. What your friend does by stealing in any country is not permissible. The story he mentioned about stealing a donkey is not known, and his inferring from the Muslims' attempt to seize Abu Sufyan's caravan is incorrect; because Allah made lawful for Muslims the spoils of war from the wealth of disbelievers, and this differs from not fulfilling a covenant and violating a condition.