The Trump administration is making headlines on its proposed 20% Mexico border tax, but the details are still unclear. According to TheStreet's politics writer Emily Stewart, the key word is "proposed." She pointed to comments from Trump's chief of staff Reince Priebus, who said the tax was among a buffet of options. "We don't know how real this is," she said. Shares of Chipotle (CMG) - Get Report and Constellation Brands (STZ) - Get Report moved lower following news of the proposed tax.