I thought that Posse Comitatus disallowed use of military on US soil. Even the Insurrection Act only allows it in cases of rebellion, terrorist attacks, insurrection, etc. The National Guard or Coast Guard can be called in, but to establish martial law is not something that these riots should provoke. I was also under the impression that martial law could only be invoked if current state resources could not handle the situation and mass, public safety concerns that threatened the popluation as a whole.
Maybe I missed a few changes in the law here or there that now allows it? Of course our current political force doesn’t care too much about the law or civil rights.