Follow this explanation. Cocaine was found in the White House by the Secret Service on a security sweep. Secret service is not law-enforcement, generally, except for counterfeiting. The cocaine was found in the absence of a search warrant. If a investigation revealed the cocaine belonged to a non-resident of the White House, that person potentially could be arrested. Now if that cocaine was connected to a resident of the White House, it cannot be used as evidence against a resident because there was no search warrant or probable cause to look for it.
Most likely scenario is that it belonged to a family member/resident of the White House.
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