Americans For Prosperity, a free-market advocacy group funded in part by the Koch network, has offered to help House Speaker Nancy Pelosi, D-Calif., pass legislation that would limit President Trump's ability to unilaterally impose new tariffs. "[W]e hope to work with your office to advance legislation to require congressional approval of any proposed tariffs," said AFP chief government affairs officer Brent Gardner and Freedom Partners Chamber of Commerce executive vice president Nathan Nascimento told Pelosi in a letter sent Friday and made public Wednesday. The group called on Pelosi to support the Bicameral Congressional Trade Authority Act, legislation jointly introduced...