It's the law to carry documentation of immigration status on you, if not a US citizen. https://www.aclu.org/know-your-rights/border-zone#are-there-limitations-

It's the law to carry documentation of immigration status on you, if not a US citizen. https://www.aclu.org/know-your-rights/border-zone#are-there-limitations-to-immigration-officials-power https://www.aclu.org/know-your-rights/border-zone#are-there-... If an agent asks you for documents, what you need to provide differs depending on your immigration status. U.S. citizens do not have to carry proof of citizenship on their person if they are in the United States. If you have valid immigration documents and are over the age of 18, the law does require you to carry those documents on you. If you are asked by an immigration agent to produce them, it is advisable to show the documents to the agent or you risk being arrested. If you are an immigrant without documents, you can decline the officer’s request. An agent may likely ask you more questions if you decline a request. No matter what category you fall into, never provide false documents to immigration officials.