As it uses the barrier key I imagine barrier=border control should actually be where you are required to physically stop (and present your passport), probably on each side of the border. There’s amenity=customs, which hasn’t been approved, but is used a few hundred times. You could have both the amenity tag and office=government, but I don’t think either is going to be rendered without a building tag on the area.
what do you mean by “I changed the tagging”? Did you change tags already present there done by other mappers?
What value was used for it before?
I also don’t understand what you mean by “asked on the wiki for the tag”. Usually the wiki is quite a bad place to ask questions. Have you tried the tagging mailing list?
help.openstreetmap.org might be another option to ask questions.