It's possible to do label:Foo in a release search, but it seems it's not possible to do laid:mbidhere if you want to search a specific label (perhaps there are two labels with the same name)

e.g. I can do http://musicbrainz.org/search?query=label%3AVirgin+AND+country%3Ajp&type=release&limit=25&advanced=1 but not http://musicbrainz.org/search?query=laid%3A49b58bdb-3d74-40c6-956a-4c4b46115c9c+AND+country%3Ajp&type=release&limit=25&advanced=1