A more thorough explanation:

Legislative immunity is a legal rule that protects lawmakers from being sued for actions taken in the course of their legislative duties. This rule is meant to ensure that legislators can perform their duties without fear of outside interference.

The Speech or Debate Clause in Article I of the Constitution grants legislative immunity to members of Congress. This protection has also been extended to state and local legislators through federal common law. Additionally, 43 states have speech or debate clauses in their own constitutions.

Legislative immunity also applies to officials outside the legislative branch who participate in the legislative process. For example, a mayor presenting a budget to the city council would be protected by legislative immunity.

However, legislative immunity does not apply to acts that are unrelated to a legislator's duties, such as making defamatory statements during a press conference. It also does not apply to acts that occur without lawful authority, such as using unconstitutional procedures to enact legislation or illegally seizing documents without a subpoena.

For example, if a member of Congress is sued for defamation because of statements made during a press conference, they would not be protected by legislative immunity. However, if the same statements were made during a legislative hearing, the lawmaker would be protected.