Shield laws in the United States are designed to protect reporters' privilege or to prevent prosecution when states’ laws differ, especially on the issue of abortion. Reporters' privilege involves the right of media to refuse to testify as to the information and/or sources of information obtained during the news gathering and dissemination process. Currently, the United States federal government has not enacted any national reporters' privilege shield laws, but most of the 50 states do have shield laws or other protections for reporters.

A shield law is a law that gives reporters protection against being forced to disclose confidential information or sources in state court. There is no federal shield law and state shield laws vary in scope. In general, however, a shield law aims to provide the protection of: "a reporter cannot be forced to reveal his or her source" Thus, a shield law provides a privilege to a reporter pursuant to which the reporter cannot be forced by a subpoena or other court order to testify about information contained in a news story and/or the source of that information. Several shield laws additionally provide protection for the reporter even if the source or information is revealed during the dissemination of the news story, that is whether or not the source or information is confidential. Depending on the jurisdiction, the privilege may be total or qualified, and it may also apply to other persons involved in the news-gathering and dissemination process as well, such as an editor or a publisher. However, shield laws do not ensure absolute protection.

The issue of whether or not journalists can be subpoenaed and forced to reveal confidential information arose in 1972 with the United States Supreme Court case Branzburg v. Hayes. Paul Branzburg was a reporter for The Courier-Journal in Louisville, Kentucky and wrote an article about the drug hashish. In creating the article, he came in contact with two local citizens who had created and used the drug. Because their activity was illegal, Branzburg promised the two individuals that he would not reveal their identities. After the article was published, Branzburg was subpoenaed by a local grand jury and ordered to reveal the identity of his sources. Branzburg refused and cited the provisions for freedom of the press from the First Amendment to the United States Constitution in his defense.

The Supreme Court decided in a five to four decision that the press did not have a Constitutional right of protection from revealing confidential information in court. The court acknowledged, however, that the government must "convincingly show a substantial relation between the information sought and a subject of overriding and compelling state interest." While this ruling did not set a precedent for journalistic rights in court, it did define a more stringent set of requirements for when a journalist could be subpoenaed in court.

This ruling was limited in nature, did not set a clear federal precedent regarding journalistic privileges from revealing confidential information, and thus has been interpreted and cited differently by courts over the years. The Third Circuit Court of Appeals, for instance, has gleaned a qualified First Amendment privilege from the Branzburg decision. In Riley v. City of Chester, the Court held that a reporter's right to protect his sources from disclosure could be overcome by a party who, by a preponderance of the evidence, demonstrated that he has made an effort to obtain the information elsewhere, that the only access to the information sought is through the journalist and his or her source, and that the information sought is crucial to the case. 612 F.2d 708 (3rd Cir. 1979).

States differ on their approach to protecting reporter's privilege. As of 2018^[update], 49 states and the District of Columbia offer some form of protections Forty states (plus D.C.) have passed shield laws. These laws vary from state to state. Some protections apply to civil but not to criminal proceedings. Other laws protect journalists from revealing confidential sources, but not other information. Many states have also established court precedents which provide protection to journalists, usually based on constitutional arguments. Only Wyoming lacks both legislation and judicial precedent to protect reporter's privilege.

Proponents of shield laws argue that they ensure that news gatherers may do their jobs to their fullest ability and that they help avoid a dichotomy between state laws and journalistic ethics, but the differences between states' laws has raised questions regarding which laws apply where in regard to national reporting. Proponents argue that a federal shield law should exist to eliminate contradictions between state laws.

Opponents argue that shield laws afford extra privileges to journalists and that no citizen should be able to ignore a court ordered subpoena. Opponents also cite problems with defining who is considered a journalist or news gatherer and who is not, and note that if journalists get special protection from the government, then they are getting special journalistic benefits from the government instead of acting in complete independence. Some opponents also argue that journalists are often forced to testify by federal courts only in cases where a federal shield law likely would not protect them anyway. Finally, the federal government may not have constitutional right to enforce a shield law on state courts.