In Blackledge, Warden, et al. v. Allison (1976), the U.S. Supreme Court ruled in favor of Robert Allison who was serving a life sentence for armed robbery and had filed a habeas corpus petition claiming that his guilty plea was not voluntary because it was based on false promises made by his attorney and the trial judge about possible leniency at sentencing. The Fourth Circuit Court of Appeals had dismissed his claim without an evidentiary hearing, but the Supreme Court reversed this decision stating that if Allison's allegations were true they would constitute a breach of due process rights under the Fourteenth Amendment. The court held that even though he pleaded guilty to avoid death penalty, if there were unfulfilled promises involved in obtaining such plea then it could be deemed involuntary despite procedural safeguards during plea proceedings. It emphasized on giving defendants opportunity to substantiate their claims when they allege constitutional violations post-conviction rather than dismissing them summarily.

In the dissenting opinion for Blackledge v. Allison, Justice Rehnquist disagreed with the majority's decision to allow a federal habeas corpus review of state court convictions based on claims that guilty pleas were not voluntary or intelligent. He argued that such reviews should be limited to cases where there was an objective factual dispute about what occurred in state court proceedings, rather than subjective assessments of whether a defendant fully understood his rights and consequences when pleading guilty. The justice contended that expanding federal review in this way undermined respect for finality of judgments and disrupted the balance between state and federal courts by allowing defendants to bypass normal appellate procedures. Furthermore, he expressed concern over potential abuse as prisoners could easily allege they did not understand their plea agreement years after conviction without any evidence supporting their claim.