What did Starr do?

He built a comprehensive case that Clinton was lying by compelling White House staff and Secret Service members to testify. After six months of negotiations to get Clinton to testify, Starr subpoenaed the president, and Clinton agreed to testify “voluntarily” for a grand jury, with his lawyers present. That precedent now hangs over the negotiations taking place between Mueller and Trump’s legal team over whether the current president will testify in the Russia investigation. “No matter how much huffing and puffing Trump’s lawyers do,” says Lanny Davis, Clinton’s former special counsel, “they cannot escape a grand jury–issued subpoena.”