The ruling potentially derails billions of dollars in subsidies for many low- and middle-income people who bought policies.
But White House spokesman Josh Earnest says while the case works its way through the courts, it has "no practical impact" on tax credits. He said the White House is confident in Justice's legal case.
Earnest says there's mixed legal opinions on whether people who buy insurance through state-based markets can get subsidies.
The ruling affects consumers in the 36 states served by the federal marketplace.