"But there are so many rules that obeying the law may become impossible. They could use a parking ticket as an excuse to deny you a visa, there is too much left

"But there are so many rules that obeying the law may become impossible. They could use a parking ticket as an excuse to deny you a visa, there is too much left up to your visa application reviewrs' discretion." Sure but in her case we don't know because she provides no details as to what the nature of her technicality was. Plenty of people leave and enter the USA everyday on work visa's. If you're on a work or student visa its made clear to you when you can and can not travel. If she decided to leave the country despite knowing that she had issues with her visa paperwork thats a pretty different situation from someone being arbitrarily refused admittance because she was a "hacker".