Final answer:
Governments may legally acquire territory through annexation or after wars, as seen in U.S. history. The U.S. Constitution provides a legal framework for this kind of expansion, allowing the federal government to control and admit new territories as states.
Step-by-step explanation:
Historically, governments have used various methods to legally take control of another territory to add it to their own. This could involve territory acquisition through annexation, where one nation declares sovereignty over another previously independent area. Annexation may be met with opposition, especially when it involves significant expansion beyond a nation's original borders.
For instance, the United States has expanded its territory through deals such as the Louisiana Purchase, acquired territories after wars (e.g., the Spanish-American War leading to the acquisition of Puerto Rico, Guam, and the Philippines), and by annexing lands like Hawaii and Alaska. In the U.S., the Constitution gives the federal government control over territories and the power to admit new states. Through Article IV Section 3, and subsequent acts like the Foraker Act and the Platt Amendment, the U.S. government has outlined the procedures for incorporating new territories and controlling them. Moreover, these acquisitions often entailed granting U.S. citizenship to the residents of these territories.