4 No. 15-3047 The suit against Craigslist having failed, the sheriff decided to proceed against Backpage not by litigation but instead by suffocation, depriving the company of ad revenues by scaring off its payments-service providers. The analogy is to killing a person by cutting off his oxygen supply rather than by shooting him. Still, if all the sheriff were doing to crush Backpage was done in his capacity as a private citizen rather than as a government official (and a powerful government official at that), he would be within his rights. But he is using the power of his office to threaten legal sanctions against the credit-card companies for facilitating future speech, and by doing so he is violating the First Amendment unless there is no constitutionally protected speech in the ads on Backpage’s website—and no one is claiming that. The First Amendment forbids a public official to attempt to suppress the protected speech of private persons by threatening that legal sanctions will at his urging be imposed unless there is compliance with his demands. E.g., Bantam Books, Inc. v. Sullivan, 372 U.S. 58, 64–72 (1963); Okwedy v. Molinari, supra, 333 F.3d at 342–44; American Family Association, Inc. v. City & County of San Francisco, supra, 277 F.3d at 1125. Central to Backpage’s case is a letter of June 29 of this year that Sheriff Dart sent both to MasterCard’s CEO and Board of Directors and to the corresponding personnel of Visa. The letter is on stationery captioned “Office of the Sheriff,” and begins: “As the Sheriff of Cook County, a father and a caring citizen, I write to request that your institution immediately cease and desist from allowing your credit cards to be used to place ads on websites like Backpage.com.” Notice that he is sheriff first, father and citizen second; notice his use of the legal term “cease and desist”; notice that he calls MasterCard “your institution,” implying