From theconversation.com: President Trump has the power to double U.S. taxes on foreign citizens and companies under a 90-year-old provision in the tax code, Section 891, if he determines they are subjected to discriminatory foreign taxes.

This provision, enacted during a tax dispute with France in 1934, allows the president to automatically double the income tax rates of affected entities, capped at 80% of their taxable income.

While this section has never been applied, its potential use is being discussed in the context of recent international tax agreements and disputes affecting American companies.