The US Constitution is an amazing document, I suggest you read it if you are an American. It's pretty short and has a lot of stuff that is useful to know, even if you aren't a lawyer (I am not). Because I am not a lawyer, I didn't word it exactly correctly.

The Fifth Amendment of the US Constitution says, in its entirety:

"No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offence to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation."

The key in this context is "No person shall ... be deprived of life, liberty or property, without due process of law." If a government agent takes that from you without due process that is a civil right of yours being abridged, at least in the US. I can't speak for other countries.