Brian Gleicher discussed with CNBC the "first sale rule," a decades-old legal provision that businesses increasingly are turning to in an effort to reduce the impact of rising U.S. tariffs. Under this rule, importers can calculate duties based on the original sale price between a manufacturer and a middleman, which is typically much lower than the subsequent sale from the middleman to a U.S. buyer. "What the rules allow you to do is use that initial sales price from the factory to the vendor to determine the final duty price," Gleicher said. He continued, saying that though in place for a long time, the rule is experiencing a surge in interest: "It's been around for a very long time but... everybody's beginning to explore it with more interest."

There are a number of requirements for the rule to be used and documentation is required to substantiate the first sale price. "If you're an importer, you need to get that first sale price. You need to have the data," Gleicher cautions. "Vendors may not want to give that information."