Robert Mueller’s first, and presumably last, public statement regarding his investigation into Russian efforts to influence the 2016 election (and the White House’s efforts to impede said investigation) effectively laid out a course of action for Congress. Reiterating his 448-page report, Mueller said that if his team were confident that the Trump had not attempted to engage in criminal conduct by obstructing justice, they would have said so.
But, they didn’t. And because Dept. of Justice policy rules out the indictment of a sitting president, Mueller’s only option was a constitutional one: rely on the system of checks and balances. So, the ball’s in Congress’ court now.