|This page in a nutshell: A sham consensus may not be relied on, because it violates a policy, a guideline, or an ArbCom decision.|
A sham consensus is either a false consensus or a wrongful consensus, or both, thus in violation of an ArbCom decision, a policy, or a guideline. A sham consensus includes an absence of a consensus where the absence has the same cause.
Do not rely on a sham consensus. However, in most cases, a consensus is not a sham even if several editors disagree with it. And even a sham consensus can change, and if that happens it may no longer be a sham. If there is a sham consensus, procedures and remedies are unchanged by this essay and may be applied as appropriate.
A sham consensus is either a false consensus or a wrongful consensus, or both. In general, a false consensus is in violation of an ArbCom (Arbitration Committee) decision and a wrongful consensus is in violation of a policy or guideline. A sham consensus includes an absence of a consensus where the absence has the same cause as a false or wrongful consensus.
Do not rely on a sham consensus.
A consensus in most cases is not a sham and it should be relied upon. A consensus with which several editors disagree is not necessarily a sham consensus, and it should be relied upon despite the disagreement. On the other hand, consensus can change, so a disagreement that is for a good reason may be a ground for consensus to change, but the existing consensus should be relied upon until it changes.
A sham consensus can change to not being a sham or be replaced by a consensus that is not a sham. If a consensus used to be a sham but is not one now, it is now not a sham consensus and it now should be relied upon.
A conflict between two or more policies, guidelines, and ArbCom decisions (such as between WP:IGNORE and another policy) may create uncertainty about whether a consensus is a sham. The presumption in that case is that it is not, in other words, that the consensus is legitimate. To decide that it is nonetheless a sham in a particular instance has to be on the basis of the particulars of that instance, which may be unique. However, in most instances, there is no relevant conflict among policies, guidelines, and ArbCom decisions.
In general, a consensus at a higher level of Wikipedia is not a sham if the only violations, if any, are against lower levels.
ArbCom decisions and policies by ArbCom are, by policy, not subject to editor consensus.
These are examples of a sham consensus. It is assumed that the policy to ignore all rules does not apply to these examples, since that policy is usually not applied to most real-life cases.
Not every editor need agree that a consensus is a sham, because your determining that a consensus is a sham is not the end of the matter. If you believe that a consensus is a sham, you may consider any of the various procedures and remedies provided for Wikipedia. This essay provides a name and a definition; this essay is not a procedure in itself.
Remedies for a sham consensus depend on why the consensus is a sham. Determine what problem is found with the consensus and find a policy, guideline, or ArbCom decision that is thereby violated. Then apply the remedy applicable to a violation of that policy, guideline, or decision in light of the policies on consensus and dispute resolution. The consensus policy alone will often be sufficiently helpful for an instance. In some instances, the policy to ignore all rules (WP:IAR) may be helpful, although that is not usually accepted as permission to disregard other policies and justification for applying IAR may be needed.
If problems are multiple, procedures and remedies may differ.
If the consensus would require changing a policy, guideline, or ArbCom decision, a possible remedy is to cause or seek—usually to seek—a change to the policy, guideline, or ArbCom decision.