Several users have suggested People of the State of New York vs. Network Associates as an instance of a DeWitt Clause being challenged, and struck down, in court. However, this case is hugely misunderstood by the media, and so these answers have been very misleading.
This case was an instance of a DeWitt Clause being challenged in court. However, the court's ruling did not directly address the issue of whether such a clause is enforceable. The court ruled on the basis of the specific wording of the Network Associates clause, and so did not generally rule on the enforceability of all such clauses.
Arguments of the Attorney General
Source: Attorney General's Argument in People v. Network Associates
Eliot Spitzer, Attorney General of the State of New York, mentions two claims in his preliminary statement for this case. The first relates to the general enforceability of a DeWitt Clause, and the second does not.
Violation of free speech and fair use:
Under New York law, a restriction that broadly chills or restricts important rights -- here, of free speech and fair use -- without a legitimate purpose, will be struck down. This Censorship Clause restricts consumers and the media alike from reviewing the software or disclosing important design or product flaws. Yet it serves no legitimate purpose, such as protecting trade secrets or confidential material.
Specifically, it misinforms consumers that the company’s prohibition
against publication of reviews or benchmark tests (itself an illegal restriction) reflects existing “rules and regulations.” Of course, no “rules and regulations” actually exist, under federal or state law -- a fact that most attorneys, including those who drafted the Censorship Clause, surely
Finally, the Censorship Clause is also void and deceptive because it conflicts with the License Agreement contained with the company’s boxed software. The boxed License Agreement, which is by its own terms the “entire Agreement between the parties,” omits the Censorship Clause. Yet the company then places that very Clause on the face of the software diskette -- even though it is by the very terms of the License Agreement void and unenforceable.
I'll elaborate a little bit on the latter point, regarding deception. The specific text that is the subject of the lawsuit is:
Installing this software constitutes acceptance of the terms and conditions of the license agreement in the box. Please read the license agreement before installation. Other rules and regulations of installing the software are:
a. The product can not be rented, loaned, or leased—you are the sole owner of this product.
b. The customer shall not disclose the result of any benchmark test to any third party without Network Associates' prior written approval.
c. The customer will not publish reviews of this product without prior consent from Network Associates, Inc.
This text was outside of the license agreement. The license agreement itself did not contain clauses (b) and (c). Furthermore, the license agreement contained a clause specifying that it (the license) constitutes the entire agreement between the consumer and Network Associates, and supersedes any prior communications related to the software.
The major claim of the deception argument was as follows: Consumers - having read the license agreement, with its clause that the entire contract between parties is contained in that license agreement, and without the "gag" clauses - will then read this text. They may reasonably conclude that the restrictions on publishing reviews and benchmarks are not part of the contractual agreement between the consumer and Network Associates, and are instead made and enforced by some other entity.
That is, the text deceptively implies that the restrictions on reviews and benchmarking are imposed not by Network Associates, but by someone else - such as the state or federal government.
Furthermore, the clauses restricting publishing reviews and benchmarking are not enforceable at all in this case (regardless of the general enforceability or legality of such clauses), because they conflict with the actual license agreement. Thus, consumers are deceived into believing that they have no right to publish reviews and benchmarks, when in this case, because of the way it is written, these clauses are not a valid contractual agreement.
Opinion of the Court
Source: PEOPLE v. NETWORK ASSOC., INC
The court rules against Network Associates. However, the ruling states that the Attorney General's claims of deception are valid. It does not directly address the first claim, of violation of free speech and fair use.
Furthermore, the ruling explicitly states that Network Associates is
enjoined from including any language restricting the right to publish the results of testing and review without notifying the Attorney General at least 30 days prior to such inclusion
which suggests that language restricting publishing of benchmarks is not necessarily prohibited. That is, Network Associates is not generally forbidden from writing a license in the future that restricts consumers' rights to publish reviews and benchmarks.