Flag of Germany
When Heinrich XI, Prince Reuss of Greiz was appointed by Joseph II, Holy Roman Emperor to rule the then-new Principality of Reuss-Greiz on 12 May 1778, the flag adopted by the "Fürstentum Reuß-Greiz" was the first-ever appearance of the black-red-gold tricolour in its modern arrangement in any sovereign state within what today comprises Germany – the Reuss elder line that ruled the principality used a flag whose proportions were close to a "nearly square"-shape 4:5 hoist/fly ratio, instead of the modern German flag's 3:5 figure.
National flag
Thus, the national flag is mentioned briefly in the Basic Law for the Federal Republic of Germany of 1949 "the federal flag is black-red-gold" (art. 22.2 "Die Bundesflagge ist schwarz-rot-gold"), but its proportions were regulated in a document passed by the government in the following year. The Flag of the United States is not defined in the constitution but rather in a separate Flag Resolution passed in 1777.