Paul traveled around and shared the gospel of jesus,and he able to that so well cause he was a roman citizen and could travel freely. But how did he,when arriving at a province,prove he is such? How did anyone in general?
Default: repeat questions are welcome, but to tide you over until someone with expertise answers exactly...
http://www.reddit.com/r/AskHistorians/comments/2486xa/in_the_west_wing_president_bartlet_says_two/
I vaguely remembered this thread (or the thread that the top respondent copied their previous answer from), and found them by searching "Roman citizen".
Remember, reddit's search feature is somewhat iffy. It doesn't do substitutions, so it will only return results for "Roman citizen," not "citizenship," not "Rome's citizens" etc. so you might have to plug in a few permutations to find results.