A disturbing recent phenomenon in Washington is that laws that strike to the heart of American democracy have been passed in the dead of night. So it was with a provision quietly tucked into the enormous defense budget bill at the Bush administration’s behest that makes it easier for a president to override local control of law enforcement and declare martial law.

The provision, signed into law in October, weakens two obscure but important bulwarks of liberty. One is the doctrine that bars military forces, including a federalized National Guard, from engaging in law enforcement. Called posse comitatus, it was enshrined in law after the Civil War to preserve the line between civil government and the military. The other is the Insurrection Act of 1807, which provides the major exemptions to posse comitatus. It essentially limits a president’s use of the military in law enforcement to putting down lawlessness, insurrection and rebellion, where a state is violating federal law or depriving people of constitutional rights.

The newly enacted provisions upset this careful balance. They shift the focus from making sure that federal laws are enforced to restoring public order. Beyond cases of actual insurrection, the president may now use military troops as a domestic police force in response to a natural disaster, a disease outbreak, terrorist attack or to any “other condition.”

Changes of this magnitude should be made only after a thorough public airing. But these new presidential powers were slipped into the law without hearings or public debate. The president made no mention of the changes when he signed the measure, and neither the White House nor Congress consulted in advance with the nation’s governors.