The Military didn't give itself anything. Their actions are prescribed by 10 U.S.C. 375 -
Restriction on direct participation by military personnel (
http://www.gpo.gov/fdsys/granule/USCODE-2010-title10/USCODE-2010-title10-subtitleA-partI-chap18-sec375/content-detail.html ), which states:
10 U.S.C.
United States Code, 2010 Edition
Title 10 - ARMED FORCES
Subtitle A - General Military Law
PART I - ORGANIZATION AND GENERAL MILITARY POWERS
CHAPTER 18 - MILITARY SUPPORT FOR CIVILIAN LAW ENFORCEMENT AGENCIES
Sec. 375 - Restriction on direct participation by military personnel
From the U.S. Government Printing Office,
www.gpo.gov §375. Restriction on direct participation by military personnel
The Secretary of Defense shall prescribe such regulations as may be necessary to ensure that any activity (including the provision of any equipment or facility or the assignment or detail of any personnel) under this chapter does not include or permit direct participation by a member of the Army, Navy, Air Force, or Marine Corps in a search, seizure, arrest, or other similar activity unless participation in such activity by such member is otherwise authorized by law.
(Added Pub. L. 97–86, title IX §905(a)(1), Dec. 1, 1981, 95 Stat. 1116; amended Pub. L. 100–456, div. A, title XI, §1104(a), Sept. 29, 1988, 102 Stat. 2045; Pub. L. 101–189, div. A, title XII, §1211, Nov. 29, 1989, 103 Stat. 1567.)
DoD Instruction NUMBER 3025.21, February 27, 2013 (The subject of these news stories claiming the Military gave itself powers) is not US Code and not US Law. It is a guidance created by directive of
10 U.S.C. 375 and can only be applied under Title 10, which pretty much states the military can only protect Gov property and maintain order in Gov installations without direct orders of the President to do anything beyond that.
It's alarm raising over something that isn't what the authors are claiming.