From 2013, but the first time I have seen this.
http://www.allgov.com/news/top-stories/new-rule-allows-us-military-to-act-without-presidents-authorization-130520?news=850072

In a major power grab of dubious constitutionality, the U.S. military last week claimed for itself the power to act unilaterally—without the authorization of the President—in case of “civil disturbances,” threatening a 200-year-old system that strictly forbids the military from becoming involved in civilian law enforcement. Seemingly innocuous in its brevity and simplicity, the new rule's chief danger lies in its vagueness:

Federal military commanders have the authority, in extraordinary emergency circumstances where prior authorization by the President is impossible and duly constituted local authorities are unable to control the situation, to engage temporarily in activities that are necessary to quell large-scale, unexpected civil disturbances.