The latest version of DoD Directive 5240.01 (DoD Intelligence Activities) dropped in late September this year, and since then every conspiracy theorist in the United States has been up in arms (pardon the pun) about section 3.3, paragraph (a)(2)(c). This directive states in this portion that UPON APPROVAL from the Secretary of Defense, US Military forces can be deployed to assist Federal, State, and Local agencies in situations where they may be expected to use lethal force [against US civilians].

Shocking, right?
No.
The fact is that this is specifically mitigated (and noted as such) by DoD Directive 5210.56 (Arming and Use of Force) of 2016 – where reasonableness of force, and scale of force is mandated, citing both Federal and SOCTUS case law.

BUT – IT IS A NEW DIRECTIVE!?!
Nah, it is effectively the same restricted authorization for the US Military to assist agencies in DoD Issuance 3025.21 (Defense Support of Civilian Law Enforcement Agencies) of 2013 with 2019 update, which spells out the same approval authority. One should REALLY investigate this policy for the number of exceptions to the rule for SecDef authorization – it might shock you.

BUT – mUh PoSsE cOMiTAtUS!?!
No again. While the PCA, (codified and revised in 18 U.S. Code § 1385) states that the US Military cannot be used to enforce the law (against civilians), there are VERY big exceptions to this law. Assistance at the behest of the State, Local, or Tribal governments, National Emergencies, Self Defense, and Insurrection/Rebellion just to name a few. The military can and has been used legally to assist in disasters, and other issues – and they have always had the right to use force as prudent under the law and per DoD directive.
Remember that Posse Comitatus was written in the aftermath of the Civil War in response to Reconstruction era local governments pressing US Army Soldiers into service to enforce local (and often Un-Constitutional) laws. Indeed, as written, it is so ambiguous that no one has ever been prosecuted for violating it.

BUT – The POTUS gonna send troops to kill errrbody!
Yeah, he could. But it would be Un-Constitutional. While the Insurrection Act (codified in 10 U.S.C. § 251-54) does allow for the President to deploy troops to put down rebellions, it only allows this when the force is requested by the State, (or) there is an actual rebellion against the Federal Government, (or) to protect Federally codified Civil Rights, AND the President must announce his intent to use the troops and order the “insurgents” to peacefully disperse before deploying troops. More HERE.
Bottom line – this is not new, un-Constitutional, or a threat to your liberty – for now.
DoD Directives are HERE.
DoD Issuances are HERE.