The next legal showdown between the Trump administration and the pharmaceutical industry is likely to be focused on the administration’s authority to tie Medicare reimbursements to foreign countries’ drug prices.

The Health and Human Services Department wants the cost of drugs that are administered in doctors’ offices to mirror the often lower prices foreign countries pay. The proposal is controversial. Accusations of “importing socialism” have swirled for months, and opponents say it’s unwise to compare the U.S. pharmaceutical market to countries that don’t have access to as many different drugs.

It’s one of the few suggestions—both from a...