On March 5, the SEC announced charges against AT&T for violating Regulation FD (Fair Disclosure), the agency’s marquee rule forbidding companies from “selectively disclosing” material information to analysts and other securities market professionals. AT&T disputes the charges, which arose out of calls with analysts in 2016. The federal courts will have final say over whether AT&T violated Reg FD. But for now—particularly in light of the SEC’s willingness to litigate five-year-old conduct—it would be fair to read the lawsuit as a warning to expect heightened enforcement interest in companies’ conversations with securities analysts, particularly when they result in changes to estimates or otherwise provoke commentary.