In general, it was the local and state governments that enforced these laws during this time, since the federal government lacked practically all powers to intervene in the states' affairs.
The answer is the Monroe Doctrine. This Doctrine was stated by the fifth President of the United States, James Monroe, on December 2, 1823, and became the foreign policy of the nation for many years.
The doctrine stated that:
●<em> The efforts of European nations to colonize land in North or South America, are considered as acts of aggression, requiring U.S. intervention</em>.
●<em> Any interference by European nations with states of North or South America would also be perceived as acts of aggression and would call for U.S. intervention</em>.
● <em>The United States would not interfere with existing European colonies</em>.
● <em>The United States would not get involved with the internal affairs of European nations</em>.
By building military bases around the world imperialist hoped to resupply navel vessels
