Originally Posted by
desconhecido
...
The inland checkpoints are a bit different. According to Supreme Court rulings on the matter, they can stop you for a brief period of time to ascertain your immigration status and that's it unless they have "reasonable, articulable suspicion" of criminal activity. So, they can ask you what your nationality is and you're probably required to answer. Any further questions or detainment are not within their authority without reasonable suspicion.
...
Be aware that "criminal activity" can include local ordinance violations, e.g., riding without a helmet, lack of lights when riding at night, riding on a sidewalk, failure to stop at a stop sign.