The lawsuit moves the dispute into federal courts after months of sniping between the Democratic-led House Ways and Means Committee, which requested and then subpoenaed the returns, and Treasury Secretary Steven Mnuchin. The outcome is likely to determine whether financial information that Mr. Trump — breaking with longstanding tradition — has kept closely guarded as a candidate and as president will be viewed by Congress and, ultimately, by the public.
But with the House and the executive branch locked in a broader struggle over access to Trump administration information and witnesses, the stakes in the tax-return lawsuit may be higher than that particular issue. House Democrats are facing resistance on a broad range of investigations that include inquiries into Robert S. Mueller III’s probe of Russian election interference, the insertion of a citizenship question into the 2020 census, and the profits gleaned from Mr. Trump’s ongoing business ventures.
In almost every instance, the Trump administration has argued that Congress’s power to access those materials is inherently limited to information that would serve “legitimate” legislative purposes — defined by the executive branch as materials primarily needed to help draft new laws.