I was in Grand Central Train Station in the AM of January 31, 2011. I have been seeing armed military personnel, who co-ordinate with police, patrolling Downtown New York City train stations. I thought this was against our US Constitution.

Are we under armed military occupation and most of us don't know it? More info:
http://starkravingviking.blogspot.com/2011/02/nyc-under-armed-military-occupation.html

Excerpt from link above:
In 1878, Congress passed a law known as Posse Comitatus that prohibited the use of military personnel or assets in domestic law enforcement. At the time, it was clear that the act was an attempt to prohibit the military from policing civilians on U.S. soil, as happened in the South under Reconstruction. What has been taking place in earnest since 9/11, however, is an attempt to erode the spirit and the substance of Posse Comitatus so that the Executive branch can effectively 'cross the rubicon' and use military personnel in domestic policing operations.