That is correct, but the warrant requirement does not follow common sense. Let me try to explain further with an example. A sends a letter to B with information in the letter that implicates C in a crime. The FBI does not have a warrant to open and search the letter. The FBI goes ahead and searches it anyway. Now, the FBI has evidence that C was involved in a crime. C, obviously, would like to challenge the search based on the warrant requirement of the 4th Amendment. It is here where the warrant requirement diverges from common sense. C does not have "standing", which is a legal term of art that basically means the court can hear and decide the case, to challenge the search because the mail was not his. Therefore, without standing, C cannot challenge the search even though the FBI did not have a warrant for the initial search. In contrast, A would have standing because he has a "reasonable expectation of privacy" in his own mail (assuming there was incriminating information against A in the letter).

No, that evidence would still be inadmissible. They could use "parallel construction" to obtain new and admissible evidence to implicate C in the crime, and could use the inadmissible information to launch an investigation they might otherwise not have. But the standing issue in this case is that Ulbricht cannot argue that his fourth amendment rights were violated by search and seizure of a third party's property.

39 U.S.C. § 4057 specifically requires a warrant for certain classes of mail and parcels, and therefore any evidence obtained in a warrantless search would be inadmissible.

Yes, that statute requires a warrant. However, the exclusionary rule is only applicable to one with a "reasonable expectation of privacy." In the hypothetical, C does not have such an expectation, and therefore C cannot challenge the admissibility of the evidence notwithstanding the statute.

Yes, you are correct. Upon rereading your hypothetical, I realized I interpreted it incorrectly.

Of course, it doesn't mean that such evidence would be especially compelling to a judge or jury in those circumstances, but that's a separate matter.

What about FedEx?

FedEx and UPS (and DHL, OnTrac, et al.) are private companies. They have the authority to open your package at any time for any reason, with few exceptions.

If I gave you a box and asked you to give it to someone else, you have the legal right to open it up and do whatever you want to it. The most I could do is sue you, civilly, for breaking a defined contract if one was in place, but for the most part I'd be limited to calling you names.

>They have the authority to open your package at any time for any reason, with few exceptions. //

Contract law in USA is that weak? They have authority? As in the law authorises anyone to access anything just by virtue of being contracted to move it, not even ownership? Contractual obligation can't override that authorisation .. are you sure?

That would mean, for example, that your taxi-driver has the right to go through your bags by virtue of you asking them to put them in their car. Or that Starbucks have a _right_ to access your laptop if you left it in the store for any length of time. Or if you park in a private parking lot the owner could break in, hot wire and drive your car around.

Or are you saying that only certain possessions are treated as if you didn't own them and only certain companies contracts are treated as null?

tl;dr http://en.wikipedia.org/wiki/Trespass_to_chattels, but yes it's a tort.

I believe uxp's point is that one would only have a civil remedy for breach-of-contract, and evidence would be admissible in a criminal court if a private carrier provided the information to the authorities with or without their consent.

But most likely, the contract with UPS/FedEx/etc would afford broad abilities to inspect and search packages for "safety and quality control" reasons, or whatever else.

Yes, that's precisely what I mean.

To take his example, if I carelessly left my laptop in a Starbucks, I have not given anyone the right to use, transport or otherwise inspect my laptop. I can assume some right to privacy over the contents of it. But if I gave my laptop to a company that specializes in transporting laptops between Starbucks locations on behalf of patrons, one can pretty much assume (given today's contract binding society) that they have some clause in the contract between us that says that they are not responsible maintaining the content of the laptop, and can at their discretion open it up and inspect the contents to be sure that they are not the facilitator in transporting illegal or "bad" data (malware source code, child porn or terrorist manifestos, etc). They don't have the explicit right to open it just because, but in giving it to them I've given them the right to do so.