What consumer protection law --- with the emphasis on "protection" -- is there which applies when there is an explicit warning, the consumer intentionally ignores the warning, and goes ahead and uses the device (fridge). and that results in a consequence?

The entire purpose of these laws is disclosure so that the consumer has a choice. The key is the disclosure so that the choice is based on understanding.

Given that large hotel chains do not undertake anything, including changing the brand of soap, without consulting lawyers and given that -- if this happened to occur in the US which it did not -- there would be some bottom feeder eager for a legal payday who would have thought of this outside of the "experts" here on FT, it's a good shot that it's a loser.

Easiest thing to do is to contact the property as OP did. If that fails, simply initiate a chargeback. Few, if any chain properties waste their time on minor chargeback issues and this means that the chargeback will be sustained.