...The Koch defense of undisclosed donors is based on the argument that throughout American history, anonymity has been essential to free speech, especially for dissenters. Rob Tappan, a spokesman for Koch Industries, wrote to me: “The rationale behind donor anonymity, which is a form of First Amendment speech, is to protect against the threat of retaliation when someone or some group takes a stand, espouses their point of view or articulates a position on issues that may (or may not) be popular with the general public or the political party in majority power. There are many precedents to this: the Federalist Papers were published under pseudonyms and financed anonymously, out of fear of retribution.”

Tappan cited two pre-Citizens United Supreme Court decisions, the 1958 ruling in N.A.A.C.P. v. Alabama and the 1995 decision in McIntyre v. Ohio Elections Commission.

The McIntyre case involved the charge that Margaret McIntyre, an Ohio resident, had violated state law by distributing, at a public forum in Westerville, Ohio, unsigned leaflets she had written in opposition to raising school taxes.

On behalf of the majority in the 7-2 decision, Justice John Paul Stevens wrote: “Under our Constitution, anonymous pamphleteering is not a pernicious, fraudulent practice, but an honorable tradition of advocacy and of dissent. Anonymity is a shield from the tyranny of the majority. It thus exemplifies the purpose behind the Bill of Rights, and of the First Amendment in particular: to protect unpopular individuals from retaliation — and their ideas from suppression — at the hand of an intolerant society.”

In N.A.A.C.P. v. Alabama, the court ruled that the demand of the Alabama attorney general for the N.A.A.C.P.'s membership list violated “the right of petitioner’s members to pursue their lawful private interests privately and to associate freely with others in doing so as to come within the protection of the Fourteenth Amendment.”...