Final answer:
Schlatt's third decree as president is not specified in historical documentation, but a relevant historical decree is President Grant's signing of the Third Enforcement Act on April 20, 1871, which aimed to protect voters and suppress the Ku Klux Klan's activities.
Step-by-step explanation:
Schlatt's third decree as president is not clearly defined within historical texts, as it seems to be a reference that doesn't align with documented history or the information provided from LibreTexts™. However, if we consider similar historical precedents, such as during the Reconstruction era, the Third Enforcement Act, also known as the Ku Klux Klan Act, could be referenced as an example of presidential decree. This act, which was signed into law on April 20, 1871, by President Ulysses S. Grant, strengthened the felony and conspiracy provisions for suffrage cases, and it gave the president the authority to suspend the writ of habeas corpus and use the army to uphold the law. Its main pursuit was to protect voters from intimidation and violence, particularly targeting the suppression activities of the Ku Klux Klan.