Nonacquiescence

In law, nonacquiescence is the intentional failure by one branch of the government to comply with the decision of another to some degree. It tends to arise only in governments that feature a strong separation of powers, such as in the United States, and is much rarer in governments where such powers are partly or wholly fused. In the context of lawsuits, executive nonacquiescence in judicial decisions can lead to bizarre Kafkaesque situations where parties discover to their chagrin that their legal victory over the government is an empty one. Nonacquiescence can also possibly lead to a constitutional crisis, given certain critical situations and decisions.
In the United States, certain federal agencies are notorious for practicing nonacquiescence (essentially, ignoring court decisions that go against them and refusing to accept their validity as binding precedent). The Social Security Administration and the Internal Revenue Service are particularly well known for such conduct. Although executive nonacquiescence has been heavily criticized by the federal courts, as well as the American Bar Association, the U.S. Congress has not yet been able to pass a bill formally prohibiting or punishing such behavior.
The U.S. Internal Revenue Service (IRS) uses the term "nonacquiescence" in its actions on decision to indicate that the IRS disagrees with a court ruling and will not follow its precedent nationwide. This does not necessarily mean that the IRS will refuse to follow the ruling of the court on that particular case; rather it means that the IRS will not apply the ruling to "other" cases. In some cases of nonacquiesence, the IRS may follow the decision's precedent within the jurisdiction of the case in question, but not apply it in other jurisdictions.