Nothing New Under The Sun ...

"In a June 16 interview with the news channel of Ukraine’s army, Armiya TV," Mason Letteau Stallings writes at The American Conservative, "an Azov commander admitted to his unit being used to prevent other Ukrainian units from retreating."

I've seen reports of this sort relating to both the Ukrainian and Russian forces in that ongoing war, almost always trotted out as if they're evidence of something new, brutal, illegal, etc.

Brutal, perhaps. But certainly not new and not likely illegal. The US armed forces have been using the technique for a long time. And in all likelihood it goes back to ancient times.

Wounded men and skulkers were stumbling rearward, seeking defilade, and beyond them the hysterical quaver of the rebel yell came through the crash of gunfire and the deeper-throated shouts of his own soldiers. Grant's first act was to establish a straggler line, including a battery with its guns trained on the road leading out of the uproar. -- The Civil War: A Narrative: Volume 1: Fort Sumter to Perryville by Shelby Foote (not an affiliate link)

That was at Shiloh in 1862. It was far from the only time the technique was used. Pretty much any time troops began to break under the strain of attack, or even when the situation seemed like that might happen, "straggler lines" were set up to force those troops back into battle.

The straggler line is a military police control line, consisting of straggler posts with connecting straggler patrols. It extends across the zone of action, normally immediately in rear of the division medium artillery position. The purpose of the straggler line is to apprehend stragglers, line crossers, and infiltrators. -- FM 101: Staff Officers' Field Manual, US Army

That's from 1955. A little bit of web search magic turns up examples of the phenomenon from at least as late as Vietnam.

There are probably quite a few uniquely negative   things to say about the Azov Brigade, but this one doesn't make the list, at least on the "unique" metric.