I think National Review mischaracterizes his famous recent statement, although I’m unsure what he meant in one crucial respect, and so am also unsure how important the mischaracterization is.
Mattis writes: “I swore an oath to support and defend the Constitution. Never did I dream that troops taking that same oath would be ordered under any circumstance to violate the Constitutional rights of their fellow citizens — much less to provide a bizarre photo op for the elected commander-in-chief, with military leadership standing alongside.”
NR writes in a subsequent editorial: “Mattis is wrong to paint all military assistance to law enforcement as a mission to ‘violate the Constitutional rights of their fellow citizens’ that necessarily ‘erodes the moral ground that ensures a trusted bond between men and women in uniform and the society they are sworn to protect.’”
I’m not sure how Mattis “paint[ed].” But he did not say that all such assistance violates constitutional rights. Nor is the claim implied. Indeed its negation is asserted. Mattis goes on to say: “At home, we should use our military only when requested to do so, on very rare occasions, by state governors.” Mattis cannot believe that all domestic uses of federal troops violate the Constitution if he’s right there painting the condition in which he thinks federal troops should be domestically used!
The editorial similarly misrepresents Mattis when it accuses him of insufficiently understanding that “the Army’s mission cannot be completely detached from the domestic tranquility of the nation it serves” and then invokes against him Eisenhower’s dispatch of the 101st Airborne Division to Little Rock in 1957. If Mattis thought that domestic tranquility and the Army’s mission could be completely detached, he would not have enumerated a criterion for their non-detachment! (It’s true that the Arkansas example goes against the letter of the Mattis criterion for using federal troops — that criterion being, again, only at the rare request of a governor. But when Mattis advocates deference to governors, surely he means law-abiding governors, not governors who are defying federal authority with force of arms. I think we can safely assume, for example, that Mattis is cool with the Union Army. Also that when he wrote his statement he was not thinking about 1957 Little Rock for the very natural reason that 1957 Little Rock sheds no light on the specifically Trumpish course of action that sparked his ire.)
These little misstatements of Mattis’s view are ultimately trivial if he meant something close to what the editorial says — if he meant, for example, that it’s necessarily a violation of constitutional rights to deploy federal troops other than at the request of a lawful governor. I doubt he meant something like that. That sounds to me like a technical and creative legal theory and, therefore, not the sort of thing a retired general and former defense secretary would vaguely propound. (He is of course also a scholar, and I wouldn’t be surprised if he did have a theory, but I think he’d have been more specific about the details in that case.) So to me the most natural reading is that he thinks the particular use of force in Lafayette Square was, in some way, excessive, unjustified, and thus a violation of rights, and that if it were to serve as a pattern for the tactics of federal troops — as, to judge by Trump’s statements at the time, it seemed it might — then those troops would be violating people’s rights. (The protesters in Lafayette Square were dispersed by the Park Police.) Mattis’s remark about governors I take to be advice of prudence rather than of law.
It is disputed whether the protests last Monday were peaceful; as far as I can tell they were mostly so. I don’t know, but I know it matters, and I expect the threshold for uses of “pepper balls” and other painful or violent weapons and tactics to be high, and I certainly expect those weapons and tactics not to be used so that the president might have a photo op, and I am outraged by the rioting, and I am choosing my words deliberately, and I am outraged not least because I agree with Mattis that the rioting does not define the protests, which are just and good, if not altogether great from the public-health standpoint; and there is no contradiction here.
As for Mattis’s broader point that the president is needlessly divisive and seems at times to think of the military as a meretricious prop (time for another parade yet?), it appears, I’ll just say, true.
Update: The Washington Post, using video footage and recorded police-radio transmissions, has reconstructed the events in Lafayette Square last Monday as well as it can. Please watch if you have a dozen minutes. The reconstruction seems consistent with my characterization of the protests except that: (1) It presents evidence that officials used rubber pellets and at least one tear-gas canister, not just pepper balls, to remove the protesters; and (2) it shows that more than the Park Police were involved in the operation, among them Secret Service, D.C. National Guard troops, and federal prison officers. Perhaps the presence of National Guard troops clarifies Mattis’s remark about his oath to support and defend the Constitution; the National Guard oath is almost identical to that of the regular armed forces, differing only in certain details pertaining to the chain of command and the Uniform Code of Military Justice. In any case, every officer or trooper present that day had taken an oath, in some form, of fidelity to the Constitution.