Story highlights International Megan's Law requires the State Department to ensure that all passports of registered offenders are marked with a "unique identifier"

Those affected will have to apply for new passports, which will be marked to indicate their conviction

Washington (CNN) The State Department began revoking the passports of convicted child sex offenders this week, in order to comply with a law passed last year. Those affected will have to apply for new passports, which will be marked to indicate their conviction.

International Megan's Law, which was passed last year to crack down on child exploitation, requires the State Department to ensure that all passports of registered offenders are marked with a "unique identifier." It also strengthens the Justice Department's ability to track offenders' international travel.

In a press release Monday, the State Department said the identifiers would be printed inside the back cover of new passports and read, "The bearer was convicted of a sex offense against a minor, and is a covered sex offender pursuant to 22 United States Code Section 212b(c)(l)."

The statement noted that registered offenders will no longer qualify to receive passport cards, since these can't be physically marked.

A State Department official told CNN Thursday that covered child sex offenders can continue to travel on their existing passports until the State Department notifies them by letter that the documents have been revoked.

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