Grammarly says the adjective federal goes before constitutional, but I'm not sure what type of adjectives federal and constitutional are.
Here's what they said:
It appears that the modifiers in the noun phrase constitutional federal one are in the wrong order. Consider changing the word order.
Nouns can be modified by more than one adjective. A specific order is followed for multiple adjectives. Review the following list to determine the correct order.
Opinion — delicious, friendly, smart
Size — big, diminutive, gigantic
Age — antique, old, youthful
Shape — angular, flat, oval
Color — crimson, magenta, scarlet
Origin — American, eastern, polar
Material — cotton, iron, plastic
Various .gov sites say that America is a constitutional federal republic:
- The web site of the U.S. Embassy in Argentina.
- The CIA's World Factbook.
... and refer to other countries as constitutional federal republics:
- Brazil (in a Human Rights Report by the State Department).
- Nepal (in U.S. Relations With Nepal, also by the State Department).