The Obama administration informed House Speaker John A. Boehner this week it will not prosecute former IRS executive Lois G. Lerner for contempt of Congress, concluding that she did not waive her Fifth Amendment rights to avoid answering questions when she was called to testify nearly two years ago. Ms. Lerner, the figure at the center of the IRS’s tea party targeting scandal, is still facing investigation over the intrusive scrutiny of conservative groups, but the decision by U.S. Attorney Ronald Machen not to pursue the contempt charge approved by the U.S. House does away with at least some of...