Courts have already ruled the NYPD's subway bag searches to be constitutional.
http://www.nyclu.org/case/macwade-v-...search-program
http://caselaw.findlaw.com/us-2nd-circuit/1252582.html
After taking those submissions under consideration and hearing closing arguments, the District Court issued an opinion in which it concluded that the Program was constitutional pursuant to the special needs exception. In its analysis, the District Court determined that the Program served a special need because it aimed to prevent, through deterrence and detection, “a terrorist attack on the subways.”
Never mind that in a 24/7 subway system with thousands of entrances, many not even staffed, there is absolutely no deterrence by these searches.