Luckily for us, most "western" jurisdictions don't allow for ex post facto prosecutions. They're actually unconstitutional in the United States. And when they are incidentally permitted outside the US, it's usually for something egregious.

Further, if something's illegal in a different jurisdiction than you are in, you aren't usually exposed to any liability, as any tourist to Amsterdam will tell you. And not having a payment record doesn't change the fact you did it and will undoubtably have left other evidence.

Once again, these are social problems that magic beans won't solve.