In a counterfactual hypothetical, if the Mexican armed forces, or an organized cartel paramilitary with command structure and uniforms, were massing near the border in preparation for a real honest to God invasion, then active duty could be warranted.

The argument they are using to avoid PCA is that it is a national emergency that threatens national security due to the cartels being a terrorist organization that infiltrates America via the southern border.

So the national security acts that were passed post 9/11, that people were warning about being a dangerous tool that would allow military deployments on US soil, are what really allows skirting of PCA.

The irony of that is that is has been the right wing that has been the loudest about the dangers of those national security acts because they were worried it would be used against them, but a knife is used to cut whoever isn’t holding it.

The way I’ve heard that they’ll get around that for now is that they will only provide logistics and clerical support and won’t be acting as armed law enforcement themselves. But watch very, very carefully for that envelope to be pushed as time goes on.