Say for the sake of argument that I have some old shrink-wrapped spaghetti packets lying around, and I'm not a huge fan of the brand. I'd like to get rid of the spaghetti somehow, but I don't want to throw it away (what a waste of food!), and I don't have a good place to put it, or a nearby food pantry willing to accept it.
Also assume that the food is not expired, that I have not tampered with it, that it is in good condition, and that it is roughly equivalent quality to the stuff on the shelf, bar age. Also assume I have documented its storage thoroughly, as one naturally does with one's pantry. If anyone were to get sick from eating this food, it is extremely implausible that it is my fault. Spaghetti is a dry good and I have handled it well.
Suppose I were to take the spaghetti into a store, non-disruptively place it on the shelf alongside an equivalent product that is still being manufactured, and leave. Have I personally violated a law? If so, what crime have I committed?
In principle, only the store stands to benefit from this exchange. I've given them back a product that they can sell a second time - it's a paltry sum, but it's certainly not costing them anything atypical. They might not be especially thrilled about my actions, but in this hypothetical I am the kind of person who would return purchased produce directly to a grocery store, so let's assume I don't care too much about that.
I do also feel the need to state I would not actually do this, and I don't at all condone it. I'm asking this question out of curiosity for how a public health situation like this would be managed legally (and in practice).