-PJ
It does apply. The regular Army cannot be used, nor can the Reserves or the National Guard if called up under Federal authority.
Only the National Guard, and only in their home state under control of their home state's Governor, and adjacent states with the permission of the adjacent state's Governor, can be used, and that's all that has been used in the past. They did not perform arrests, they only acted as additional clerks to process paperwork.
https://www.thoughtco.com/posse-comitatus-act-military-on-border-3321286