Mailau, who denied an act of foul play, was found guilty by the judicial officer and initially banned for three weeks.
That was reduced to two because of his excellent disciplinary record but he will miss Tonga’s last two group matches against Argentina and New Zealand.
Tonga lie second in Pool C, three points behind leaders New Zealand.
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Mailau has 48 hours to appeal.
(Reporting by Ed Osmond)
