just like customs in waking consciousness, it represents the passage between two states; a customs office in a dream represents the transition from one state to another and the customs officer verifies the dreamer's ability to cross this border of perception.
wandering or problematic relations and conflicts at customs: the unprepared state of the dreamer's consciousness for other than the currently lived state (e.g. not understanding the first experiences of exceptional states of consciousness, not understanding the difference between the emotional and instinctual level, etc.).
friendly customs officials, passing through customs without being checked; the dreamer is able to clearly perceive the two different levels of experience.