In the case of Mitchell v. Forsyth, former Attorney General John N. Mitchell was sued by William D. Forsyth for authorizing a warrantless wiretap on his phone during the Vietnam War era as part of domestic surveillance efforts to identify individuals who were leaking classified information to anti-war activists and foreign agents. The Supreme Court had to decide whether or not Mitchell could claim absolute immunity from civil suits in his role as Attorney General when national security issues were at stake. The court ruled 5-4 that while Cabinet-level officials like the Attorney General do have some qualified immunity protections against lawsuits related to their official duties, this does not extend into an absolute immunity protection for all actions taken in office, especially where constitutional rights are concerned. Therefore, it held that Mr. Mitchell could be sued personally for damages if he knowingly violated someone's Fourth Amendment rights against unreasonable searches and seizures by authorizing illegal wiretaps without a court order.

In the dissenting opinion for Mitchell v. Forsyth, Justice Brennan disagreed with the majority's decision to grant absolute immunity to Attorney General John N. Mitchell for his role in authorizing a warrantless wiretap during his tenure under President Nixon. The dissent argued that this ruling contradicted previous decisions of the Court which had only granted such immunity sparingly and in cases where it was essential for preserving the effectiveness of government operations. In contrast, Brennan contended that there were no compelling reasons why an official who knowingly violates constitutional rights should be shielded from liability simply because he holds high office or has national security responsibilities. He also expressed concern about how this decision could undermine public trust by creating a perception that those at top levels of government are above the law.