In the United States, illegal immigration is a violation of criminal and administrative law, but not civil law.
Criminal vs Civil vs Administrative law
People that enter the United States without being inspected by an immigration officer at a port of entry can be criminally charged with 8 U.S.C. § 1325 : US Code - Section 1325: Improper entry by alien. Also under 8 U.S.C. § 1182, they are considered inadmissible under administrative law and can be processed for Removal from the United States.
Individual citizens cannot sue an illegal alien in court for having entered or being illegally present in the United States.
https:// www.law.cornell.edu/uscode/text/8/1325
Federal law is created at the national level, and applies to the entire nation (all 50 states and the District of Columbia), and U.S. territories. The U.S. Constitution forms the basis for federal law; it establishes government power and responsibility, as well as preservation of the basic rights of every citizen.
State law is the law of each separate U.S. state and is applicable in that specific state. The state law applies to residents and visitors of the state, and also to business entities, corporations, or any organizations based or operating in that state.
When a state law is in direct conflict with federal law, the federal law prevails. A state law can afford more rights to its residents than federal law, but is not meant to reduce or restrict the rights of a U.S. citizen.