New rules allow investigators to hold domestic-terror suspects longer than others without giving them a Miranda warning, significantly expanding exceptions to the instructions that have governed the handling of criminal suspects for more than four decades.  
 
The move is one of the Obama administration's most significant revisions to rules governing the investigation of terror suspects in the U.S. And it potentially opens a new political tussle over national security policy, as the administration marks another step back from pre-election criticism of unorthodox counterterror methods.