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Yus. that other country depending on their laws can take the child away from the guardian. Just like when interracial dating was legal in one state in the US but then they travel to another state in the US it was illegal and they were sent to jail.
One of the Hague Conventions is of importance in this.
https://en.wikipedia.org/wiki/Hague_Adoption_Convention
Other than that it's a question that doesn't have a single answer. Each nation will have it's own slant on this issue. If you want to be really bored, here's the relevant bits from UK law. :)
Might that have been many years ago?