I base my statement on the Federal Rules of Civil Procedure as well as court precedent.
Rule 26. General Provisions Governing Discovery; Duty of Disclosure
(a) Required Disclosures; Methods to Discover Additional Matter.
(1) Initial Disclosures.
Except in categories of proceedings specified in Rule 26(a)(1)(E), or to the extent otherwise stipulated or directed by order, a party must, without awaiting a discovery request, provide to other parties:
(A) the name and, if known, the address and telephone number of each individual likely to have discoverable information that the disclosing party may use to support its claims or defenses, unless solely for impeachment, identifying the subjects of the information;
(B) a copy of, or a description by category and location of, all documents, electronically stored information, and tangible things that are in the possession, custody, or control of the party and that the disclosing party may use to support its claims or defenses, unless solely for impeachment;
Rule 26 (a)(5)(b)(1) says:
Parties may obtain discovery regarding any matter, not privileged, that is relevant to the claim or defense of any party, including the existence, description, nature, custody, condition, and location of any books, documents, or other tangible things and the identity and location of persons having knowledge of any discoverable matter. For good cause, the court may order discovery of any matter relevant to the subject matter involved in the action. Relevant information need not be admissible at the trial if the discovery appears reasonably calculated to lead to the discovery of admissible evidence.
The Fourth Amendment notwithstanding, the courts have allowed discovery where it is not prohibited by certain restrictions. For example, if a corporation makes it known that ESI on the corporate network is not private, the courts have allowed admissability of evidence recovered. See American Postal Workers Union, Columbus Area Local AFL-CIO v. United States Postal Serv., 871 F.2d 556, 59-61 (6th Cir. 1989). Also United States v. Bunkers, 521 F.2d 1217, 1219-1221 (9th Cir. 1975), etc, etc.