The house and congress recently passed legislation that was in turn signed by President Obama, which will make it significantly more difficult for those who were convicted of a sex offense against children to travel. The law, known as International Megan's Law, will require those who have been convicted of sex crimes against minors to carry special passports in which their status as registered sex offenders will be marked with conspicuous identifying marks.
The sponsor of the legislation believes that it will help to stop "sex tourism", where persons leave the country to abuse children in more tolerant countries. While this is an admirable goal, and virtually no one will support sex tourism where children are the victims of pedophile adults, this probably creates far more problems than it solves. Arguably it will act to virtually prohibit those who are convicted of sex offenses against children from travelling outside the united states.
The author of this recent Slate article that can be read here does a great job of discussing the fact that most sex offenders have a very low rate of recidivism, and already face massive challenges in being forced to register as sex offenders and the accompanying challenges that brings.