Why You Can't Legally Bring Mexican Bologna Into The US - Tasting Table
Briefly

Cross-border movement of agricultural products is tightly regulated to prevent the introduction of pests and diseases. Even cooked pork products such as bologna and ham from Mexico can be restricted because of risks like classical swine fever. Mexican pork can enter the United States only with veterinary documentation certifying the products are disease free. Travelers must declare foods at the border so customs agents can determine permissibility. Permissible items may be allowed entry, prohibited items can be left behind, and failure to declare restricted items can result in civil penalties.
Various fruits and vegetables have been prohibited from entering the U.S. at different times, typically in an attempt to keep pests and diseases from entering the nation's agricultural system. Presently, even cooked products like bologna and ham from Mexico are restricted due to the potential of harboring diseases like classical swine fever. This does not prevent the import of Mexican pork products into the U.S., but the law requires that these products be accompanied by veterinary documentation showing them to be disease free - not the sort of thing that someone with a trunk full of bologna is likely to have on hand.
For your own safety, you should always declare foods at the border, where customs agents can tell you whether or not the items are permissible to bring into the country. If they say it's okay, then you know you're in the clear. If not, you can leave the prohibited items there and continue onward. The only trouble comes if you fail to declare something that you are not allowed to bring into the country. In that case, you may be subject to civil penalties.
Read at Tasting Table
[
|
]