A more thorough explanation:

The Walsh Act is a law that was first passed in 1926. It gives federal courts the power to force U.S. citizens or residents who are living abroad to come back to the United States and testify in criminal cases. This law also allows the courts to request that these individuals produce documents or other items that may be needed as evidence.

For example, if a U.S. citizen is living in France and is suspected of committing a crime in the United States, the Walsh Act could be used to force that person to come back to the U.S. and testify in court. The law could also be used to request that the person produce any documents or other items that may be needed as evidence in the case.

The Walsh Act is most commonly used in criminal proceedings, including grand-jury proceedings. This means that it is often used to gather evidence in cases where someone is suspected of committing a crime.