Immigration Laws are laws which apply only to non-citizens like students, scholars and others. INS or Immigration and Naturalization Service is responsible for enforcing immigration laws. It is a part of U.S Department of Justice with its Head quarters in Washington D.C.
Official documents you must keep as evidence of your legal status in U.S.
Form 1-20 or I AP 66 (certificates of eligibility) for students and scholars
Form 1-94 -Arrival Departure Record which is issued at the point of entry into the U.S
Records of Immunization taken
Medical or other Insurance papers