I remember a friend asking me if I could check the visa application process to the U.S. because he didn't really understand. The form was DS 160, if I recall.

Here is a sample:

http://photos.state.gov/libraries/jamaica/231771/PDFs/DS-160...

Some questions from page 38:

"Are you coming to the United States to engage in prostitution or unlawful commercialized vice or have you been engaged in prostitution or procuring prostitutes within the last 10 years?"

"Do you seek to engage in espionage, sabotage, export control violations, or any other illegal activity while in the United States?"

"Do you seek to engage in terrorist activities while in the United States or have you ever engaged in terrorist activities?"

I mean, I'm sure there's a rationale behind these questions.. maybe in a "plausible deniability" way.. but they're funny.

The problem is that sometimes, one cannot know if they violated a law. There was a video of a lawyer asking people not to talk to the cops where he addressed this point.