Cuáles crees que son las causas por las que los gobiernos ponen restricciones a las migraciones

a big wall across the mexican border so no drugs, terrorist, or illegal immigrants can come through : )    

the national congress's powers over the states were specific and definite: it had the sole power to negotiate treaties, declare war, and make peace. all powers not granted to congress were reserved for state governments. congress had no power to levy taxes, for example.

once he became head of state in 1915, venustiano (his name was not victoriano) carranza was able to implement some of his ideas, such as the drafting and the promulgation of the mexican constitution of 1917, which is still the current constitution of that country.