For the past five years, beginning with his first presidential campaign, Barack Obama has promised that his government would be the most open and transparent in American history. But the Obama administration's steadily escalating war on leaks, the most militant I have seen since the Nixon administration, has disregarded the First Amendment and intimidated a growing number of government sources of information — most of which would not be classified — that is vital for journalists to hold leaders accountable.

The White House has tightened its control over officials' contacts with the news media, and federal agencies have increasingly denied Freedom of Information Act requests on the grounds of national security or protection of internal deliberations.

The secret and far-reaching subpoena and seizure of two months of records for 20 Associated Press phone lines and switchboards — used by more than 100 AP reporters in three news bureaus and the House of Representatives — is especially chilling for journalists and their sources. The effort was reportedly part of a Justice Department and federal grand jury investigation of an AP story from May 7, 2012, revealing the CIA's success in penetrating a Yemen-based al-Qaida group that had developed an "underwear bomb" to detonate aboard U.S.-bound aircraft.