in order to play an artifact.Commentary
The constant ability of Customs Office creates a play restriction that must be met before an artifact can be played. If a player has no Æmber in their pool, that player would not be able to play an artifact with an Æmber bonus icon, as the bonus icon will not resolve until the Artifact is in play.
Source: Timing Chart
this card's ability specifically uses the word Pay, and therefore Æmber used to satisfy this card's cost is not considered to be lost to a steal effect.
Similar to Tentacus, multiple copies of Customs Office require your opponent to pay one Æmber for each copy of Customs Office in your play area before an artifact can be played. If your opponent is unable to pay the full requirement, they pay nothing.
Source:
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