Below is the text of a National Lawyers Guild (NLG) pamphlet on your rights if you are questioned by police, FBI, custom agents or immigration officers. The pamphlet is available in pdf form on the NLG Web site.
WHAT RIGHTS DO I HAVE?
Whether or not you're a citizen, you have rights under the United States Constitution. The Fifth Amendment gives every person the right to remain silent: not to answer questions asked by a police officer or government agent. The Fourth Amendment restricts the government's power to enter and search your home or workplace, although there are many exceptions and new laws have expanded the government's power to conduct surveillance. The First Amendment protects your right to speak freely and to advocate for social change. However, if you are a non-citizen and are deportable, DHS* can target you based on your political activities.
Constitutional rights cannot be suspended--even during wartime.
*The Immigration and Naturalization Service (INS) is now part of the Department of Homeland Security (DHS) and has been renamed and reorganized into: 1. The Bureau of Citizenship and Immigration Services (BCIS); 2. The Bureau of Customs and Border Protection (CBP); and 3. The Bureau of Immigration and Customs Enforcement (ICE). All three bureaus will be referred to as "DHS" for the purposes of this pamphlet.
WHAT IF POLICE, FBI, OR IMMIGRATION AGENTS CONTACT ME?
Q: Do I have to answer questions?
A: You have the constitutional right to remain silent. It is not a crime to refuse to answer questions. It is a good idea to talk to a lawyer before agreeing to answer questions. You do not have to talk to anyone, even if you have been arrested or are in jail. Only a judge can order you to answer questions. There is only one exception: in some states outside of California, it can be a crime to refuse to give your name if you have been detained. You do not have to show ID or give any other information such as your address or immigration status...
http://socialistworker.org/2010/10/08/know-your-rights