If your boss absolutely forbids you from going on a trip, this is an example of an insuperable obstacle to you going on the trip.
Origin of insuperableMiddle English ; from Classical Latin insuperabilis
Origin of insuperableMiddle English, from Old French, from Latin &imacron;nsuper&amacron;bilis : in-, not; see in–1 + super&amacron;bilis, superable; see superable.
(comparative more insuperable, superlative most insuperable)
From Latin insuperabilis