[microgood]

Not true. If the government searches everyone, for example at airport screening, or sobriety checkpoints it is permissible and has been upheld by the courts. You can refuse to be searched at airport screening points, but you will be denied boarding. You can refuse to be greeted at a sobriety checkpoint, but you will lose your driver's license.

Those are special exceptions granted by the Supreme Court to the 4th Amendment and are related to public safety (like drug testing certain occupations and not others). This situation is not a public safety issue.

[CholeraJoe]

There is an implied consent in driving and traveling by air - in exchange for allowing me to drive, I will consent to sobriety checkpoints or giving a breathalyzer if stopped for speeding. In exchange for allowing me to travel by air, I consent to allowing my person and luggage to be searched.

This law legislates an implied consent into welfare payments. In exchange for receiving welfare, the recipients agree to be periodically tested for drugs.

Search with the consent of the owner can reveal evidence admissible in court.