Here are the two laws that Teixeira is accused of violating.

The two laws cited in the F.B.I.’s criminal complaint against Jack Teixeira, the 21-year-old National Guard airman accused of leaking classified documents, center on protecting government secrets.

Patrick M. Lueckenhoff, an F.B.I. special agent, told a federal judge on Friday that there was probable cause to believe Mr. Teixeira had violated two parts of Title 18 of the federal code: Section 793 and Section 1924.

Section 793, better known as the Espionage Act, is part of a World War I-era law that criminalizes the mishandling of closely-held information related to the national defense that could be used to harm the United States or to aid a foreign adversary. A conviction carries a prison sentence of up to 10 years per violation.

Mr. Lueckenhoff said Mr. Teixeira had violated two separate provisions of Section 793. One covers the unauthorized retention of such information, and the other covers the transmission or disclosure of the information to a person who is not authorized to receive it.

Section 1924 criminalizes the mishandling of classified information. It is punishable by a fine or a prison sentence of up to five years, and it is worded differently from Section 793 in two important ways.

First, Section 1924 makes it an offense for someone with access to classified documents to remove them without authorization and with the intent to retain them at an unauthorized location. But it does not address the act of giving such documents to other people who are not supposed to see them.

Second, Section 793 was enacted before the modern classification system for protecting government secrets was created, so it does not refer to classification status — like whether a document is marked secret or top secret.

By contrast, Section 1924 specifically refers to classified information, so prosecutors would have to prove to a jury that a mishandled file was classified as an element of proving that offense.