Free speech is crucial to our democracy. And after explicitly backing candidates or initiatives, essential to free speech is financial privacy. It’s good to know, for example, who is giving money to a political candidate because politicians have direct control over our lives. But if non-profit groups and foundations cannot keep donor lists secret, then the donors can be harassed into ending their gifts, silencing the groups’ work.

That’s why we cheer federal Judge Manuel Real’s decision this month to keep secret the donor lists of the Americans for Prosperity Foundation. Reported the Wall Street Journal, since 2013 California Attorney General Kamala Harris “has been demanding that nonprofits provide unredacted donor names if they want to solicit donations in the state,” but the judge “declared her disclosure requirement an unconstitutional burden on First Amendment rights.”

Ms. Harris had claimed the lists were needed to look for violations of state law. Judge Real replied, “[O]ver the course of trial, the Attorney General was hard pressed to find a single witness who could corroborate the necessity of Schedule B forms in conjunction with their office’s investigations.” The Schedule B forms list contributors.

Ms. Harris said the forms would be kept private. But the judge found, “[T]he Attorney General has systematically failed to maintain the confidentiality of Schedule B forms.” According to the Journal, Ms. Harris’ website contains 1,400 Schedule B forms.

The IRS already closely monitors charities to make sure they comply with proper non-profit rules.

Unfortunately, Ms. Harris also has been investigating ExxonMobil on whether it “lied to the public and shareholders about the risks of climate change, and whether the company’s statements over the years constitute violations of securities laws and other statutes,” as the New York Times reported.

But the oil giant also has free speech rights and can express itself as it wishes.

Having been chastened over Schedule B disclosure, we urge Ms. Harris, who is running for the U.S. Senate, to drop her investigation of ExxonMobil. As Thomas Jefferson said, “I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it.”