the article is poorly written - it does not provide any facts. but, if the waiter expressed the allergies with a sufficient level of force, then it falls upon the cook.
it is very difficult to see how any judge in any liberal democracy could legally fault the victim for forgetting their epipen.
but, a lot of how you react to this is going to depend on what kind of social contract you feel is best applied. i'm an advocate of the proudhonian social contract, but less so of the one promoted by rousseau. i do consequently think that the waiter has a moral, legal and social responsibility to ensure that he does not poison anybody, and that he should face collective punitive action by society should he not uphold that social contract.
http://www.cbc.ca/news/canada/montreal/sherbrooke-waiter-arrested-salmon-allergic-customer-negligence-1.3707667