Usually, there are several bodies responsible for enforcing domestic law in United States of America. However, there are instances that government may decide to use military to enforce domestic laws. U.S constitution provides various occasions when the land and naval forces may intervene in domestic law enforcement duties. These include the event of insurrection, usurpation or cases of invasion. The main aim of using the military in these events is to protect the government authority.
Involvement of military forces is provided by several acts of the Congress and other constitutional exemptions. The Congress or U.S President may alter the law to allow the use of military in civilian matters. It implies that involvement of military is only permissible when there is express authorization from the president or the Congress. In case of insurrection, the president uses the military to suppress the unfortunate event. Note that the U.S constitution gives this power to the Congress and the President only. The aim of such restriction is to prevent abuse of military power and integrity.
U.S defense may also partner with the police in providing civilian protection. In this case, the respective department provides the local, state or federal police with intelligent information, personnel support or even the equipment to fight crime. All these require express authority from the president and only in excessive events. This kind of military involvement becomes necessary when the police fail to deal with extreme violation of the law by the public. In this regard, the police may not have sufficient ability to deal with extreme situation.
Charles Doyle,and Jennifer K. Elsea. “The Posse Comitatus Act and Related Matters”: The Use of the Military to Execute Civilian Law,
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