The problem is that post cbp is considered U.S. territory
It's even scarier than that, as I discovered during an incident at Dublin. It's a weird limbo.
It remains host-country territory,diplomatically and legally, however:
4. Within the preclearance area, the Host Party shall:
...
(d) authorize the Inspecting Party's preclearance
officers who act on reasonable grounds to use as much
force as is necessary to perform their preclearance
duties under the Agreement. The preclearance officer
may not use force that is intended or is likely to
cause death or cause grievous bodily harm, unless the
officer believes on reasonable grounds that it is
necessary for self-preservation or the preservation of
anyone in the preclearance area from death or grievous
harm.
So basically Ireland ( or Canada or whomever ) grants US officials physical power over host-country citizens on host-country territory.