The Federal Trade Commission showed a wise level of restraint last week when it ended an antitrust investigation of Google without filing a lawsuit against the company. The commission’s 5-0 decision to let Google off doesn’t mean that the Internet search giant isn’t, as critics allege, tweaking search results in ways that direct more eyeballs to its ads and its own Web content. But it does mean that not all obnoxious behavior by dominant firms is illegal. It also means that in a fast-changing industry, government antitrust action isn’t the only way — or even the most likely way — for such behavior to be punished.

Google is flexing its muscles, and it may well be engaging in what the FTC calls “search bias.” Search “BOS-LAX,” and the most prominent links on the results page go to paid advertisers and Google’s own flight-search service. In recent months, there has been a rash of complaints that the company is nudging users toward its Google Plus social network by offering more prominent placement in search results to people and businesses who do.