The law meant that able-bodied Americans now had protection against economic persecution for pre-crimes, so to speak, detailed in their mutated genes.

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Descendants of Spaniards who left the country for fear of political persecution or economic hardship between 1936 and 1955 will now be able to apply for nationality before 2011.

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The assumption is that people genuinely in fear of persecution will put up with these restrictions, while economic migrants might be deterred.

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