Law enforcement officials announced last spring that they were pursuing fraud investigations against the world's largest oil company, ExxonMobil. Fossil fuel companies ... deceived investors and consumers about the dangers of climate change," [Attorney General Maura] Healey said at the time. Now those words are being used against Healey, in a lawsuit filed by ExxonMobil. In a stunning offense-is-the-best-defense legal strategy, the company is ... saying the Massachusetts Democrat's investigation violates their free speech and other constitutional rights. In its legal battle to shut down her investigation, ExxonMobil has demanded that she testify about her efforts and provide documents from her office. Healey contends the corporate response is unprecedented: Not only is [ExxonMobil] refusing to comply, it is demanding an investigation of the investigating agency. "They took the tack of trying to shut down this investigation by suing us," she said. When Healey issued subpoenas seeking ExxonMobil's documents on climate change dating to the 1970s, she was "abusing the power of government to silence a speaker she disfavors," lawyers for ExxonMobil wrote in their June lawsuit against her, alleging a violation of the company's rights. And they criticized the stories that prompted the investigation: Reports published in 2015 ... suggested ExxonMobil had encouraged climate change confusion for years, despite its own research documenting the risks.