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Pluralistic: "If buying isn't owning, piracy isn't stealing"
(pluralistic.net)
This is a most excellent place for technology news and articles.
That would depend on the terms of sale.
Unlikely as what you’re implying sounds like a get-out clause in favor of the trader which is not valid.
https://europa.eu/youreurope/citizens/consumers/unfair-treatment/unfair-contract-terms/indexamp_en.htm
Without details of the hypothetical scenario made here, we cannot know if that's the case. If the ticket purchaser was unable to see the circus because their flight home was delayed, the circus has no obligation to refund them. If attendance of "Circus 2" is offered to the purchaser due to the cancellation of "Circus 1" under the conditions of the original ticket purchase, then it's unlikely to be an unfair contact.
There are all kinds of details missing here that we can freely speculate about.