In the case of Lambert v. California, Virginia Lambert was convicted for violating a Los Angeles municipal ordinance that required felons to register with the city within five days of their arrival. Lambert, unaware of this law due to her lack of knowledge and understanding about it, failed to comply and was subsequently arrested and charged. The U.S Supreme Court overturned her conviction in a 5-4 decision stating that convicting someone for failing to act when they were not aware they needed to do so violated due process under the Fourteenth Amendment. This ruling established an important precedent: actual knowledge or notice is necessary before punishing failure-to-act crimes where there's no reason for individuals involved being aware they're committing illegal activities.

In the dissenting opinion for Lambert v. California, Justice Tom C. Clark argued that ignorance of law should not be a defense and that it is every citizen's duty to know the laws they are subject to. He contended that allowing such a defense would open up countless opportunities for people to claim ignorance as an excuse for breaking the law, which could potentially lead to chaos in society and undermine respect for legal institutions. Furthermore, he pointed out that Lambert had lived in Los Angeles long enough (seven years) before her arrest under this ordinance; thus she had ample opportunity to familiarize herself with local regulations. Therefore, according to him, there was no violation of due process because everyone has a responsibility towards knowing and understanding their obligations under the law.