The general rule is that the federal government may not be equitably estopped from enforcing public laws, even though private parties may suffer hardship as a result in particular cases. Office of Personnel Management v. Richmond, 496 U.S. 414 (1990); Heckler v. Community Health Services of Crawford County, Inc., 467 U.S. 51 (1984); INS v. Miranda, 459 U.S. 14 (1982); Schweiker v. Hansen, 450 U.S. 785 (1981); Federal Crop Ins. Corp. v. Merrill, 332 U.S. 380 (1947). No decision of the Supreme Court holds that equitable estoppel lies against the government in any circumstance. However, in several instances the court has expressly declined to determine whether the government could be estopped in a case involving serious affirmative misconduct by government employees. See, e.g., Heckler v. Community Health Services, supra; INS v. Miranda, supra.
The Supreme Court has made it clear that before an estoppel will lie against the government a private party must at a minimum demonstrate that all the traditional elements of an estoppel are present. See Heckler v. Community Health Services, 467 U.S. 51, 59-61 (1984). An estoppel cannot be asserted against the government on the basis of oral advice, Heckler v. Community Health Services, supra; nor can the government be estopped merely because it is engaging in "commercial undertakings." Federal Crop Ins. Corp. v. Merrill, supra at 383 n.1 (1947). The rule against estopping the government does not depend upon a showing of impact on the federal treasury, INS v. Miranda, supra; Montana v. Kennedy, 366 U.S. 308 (1961); nor does it depend on whether a single agent of the government, or an entire agency, has engaged in misconduct. See, e.g., INS v. Miranda, supra; Schweiker v. Hansen, supra.