First question, is this person a US citizen? Then, can this person get a passport? If yes to both then returning to the US will not be a problem. The person might get pulled for closer inspection
, body search or maybe luggage checked for child porn or similar.
As far as travel to other countries, depends. Contrary to popular believe, outside the US all the countries are different and have different laws. Some countries, Australia
for one, require you to fill in a form that includes questions about your legal
background. I think a felony arrest will exclude you from entry. Canada
I think may be similar. Other countries, if you have US passport then I guess the figure if the US lets you travel then they will let you in.
You will need to research
each one separately.