Security Practices by Private Companies

My question involves business law in the state of: Nevada

"The legal construct for commercial enterprises permits private companies to enact any appropriate security practices it deems necessary" This is a verbatim quote from a private enterprise. This is a testing site that now forces a search of the person taking a test. My question is, is this policy legal and I feel like you are being subjected to a search without any cause, in other words you are assumed to be guilty till you prove otherwise. Please note that this not a high security area or entity, it is a mere testing site. I thought 4th amendment forbids such activity. Any comments will be appreciated.

You plucked that out of what government regulation?

Quote:

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Quoting Mr. Knowitall

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You plucked that out of what government regulation?

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That is what I am trying to find out, if there is such a regulation. This is being quoted by the legal counsel of this private enterprise. I questioned their policy and he is asserting that they have the right to do so and I am trying to get some legal opinion on this. Any comments will be appreciated. Thanks