It’s tough to keep track of all the U.S. industries now threatened by the tariffs the Trump administration has teased, announced and implemented this year, but one in particular should worry readers of this and other newspapers. Since March a tariff of up to 30% on Canadian uncoated paper has raised the price of newsprint, making it difficult for cash-strapped newspapers to circulate their work. As if limiting economic freedom weren’t enough, the administration is also undermining Americans’ freedom of expression with this needless tax on journalism.

The...