Border Crossing Info Update
The rules for ammunition, drug paraphernalia, Cuban made products and most of the restricted goods are still illegal and not allowed to be brought across the border. Customs and Border Patrol has a very long list of items that can not be brought across the border we just wanted to go through a few with you. Some people try and bring back items into the US that are deemed as illegal (absinthe, fireworks) and CBP says that these are still a no go. The importation of absinthe is not allowed by the U.S. Food and Drug administration. If you are trying to bring absinthe across the border, the content must be "thujone free", which means it must contain less than 10 parts per million of thujone. The terms "absinthe" is not allowed to be in the brand, the term absinthe is not allowed to be on the label and, or the artwork/graphics.
If you wanted to try and bring an automobile back across the border, you need to make sure that the fuel emission requirements by the Environmental Protection Agency are met. Almost all cars, vans, and SUVs bought outside of the country (aside from Canada) don't meet the standards and need to be fixed in order to meet them. Bottom line, there are lots of things that you shouldn't be bringing across the border, or simply aren't recommended to ship across to the US and if you ever need a reference you can know scan this wonderfully convenient code for your iPhone:
If you scan the one on the left it takes you to the page with all the information about what is Prohibited and Restricted in the USA and then if you scan the one on the right it'll take you to the place where you can see what is Prohibited and Restricted in Mexico. If these links don't work, or you don't have an iPhone, here is the link for USA and here is the link for MEXICO.