Agree, the regulations are pretty clear that if it says wild caught, it has to be wild caught.
But these regulations are routinely unchecked, and barely enforced. Even in rare instances when they are, the penalties are not severe. Given the drastic differences in toxin content between wild and most farmed raised salmon, and that misleading people in this way causes them to spend money against their will to put known carcinogens and other toxins in their body, and, to boot, does so in a part of the world where millions already die from cancer, the enforcement is wildly out of sync with the harm or importance.
Try calling a few stores which buy their fish from a supplier, and sometimes they will say they verify wild caught by asking the supplier, and relying up what the supplier says. Trader Joes is one such store, which is always goes by the maxim "trust us, as we trust what others tell us."
One argument is that more enforcement is very costly. But a small amount of enforcement combined with penalties in accord with the crime, would solve the problem. It is ironic -- in the U.S., at least, a country that has overzealous laws and penalties in many instances -- that we tend to look at this idea of flat out deceiving people [which is exactly what claiming farm raised fish as wild caught is, there's no gray area] about things they put into their bodies that contribute to mortality and serious disease, as not that big of a deal.
Given the enormous difference in price between wild and farm raised, the enormous (and increasing) market for fish, and the lax oversight and lack of attention to the importance of rules requiring companies not to lie to consumers about the content of the substances which they are selling to consumers to put into their bodies, it is, unfortunately, likely that a lot of fish is mislabeled.
And will continue to be until we get serious about the issue; which perhaps as a practical matter needs to start with informed, and very vocal, citizens who don't just join tea parties and listen to extensive rhetoric from a wildly uninformed Sarah Palin or GLenn Beck about how great freedom is, but insist upon those aspects of responsibility that respect individual freedoms rather than trounce upon them through deception.
Even for a libertarian, there are things we need to do together because it is either highly impractical or impossible to achieve individually. Such as, for instance, national defense, environmental protection, and integrity in food labeling -- not what ultimately determines food necessarily -- but labeling regarding what the food actually is, and its accurate content. Two of the three on this list, ironically, are things tea party leaders or anti government types seem to often scoff at. Which raises the question (as to other things): How much of this is true belief, and how much is rampant misinformation through an ineffective and cow towed media, and leaders who achieve their position through persuasive and nice sounding phrases but with terrible misunderstanding of the basic issues, concepts, facts, and science?