So, just to understand, would you be against prosecuting pedophiles that go abroad in a country where having underage sex is not a crime to rape children? Over the course of human history it was perfectly normal to have sex with underage people, so it seems a rather fitting comparison.
That becomes a way more interesting hypothetical if you strip away the emotionally charged language.
Let's say a twenty-year-old Californian goes to Canada, meets a 16-year-old, and they have sex. This is (according to wikipedia, don't rely on me for legal advice!) illegal in California and legal in Canada.