The 35-year-old former Kangaroos and Wallabies outside back last played professionally in Australia with the Newcastle Knights in the 2014 NRL season.
Sanctioned by USA Rugby and World Rugby, the Professional Rugby Organization was launched in November to give North American its first professional rugby union competition.
The first season begins next month and runs 16 weeks till the end of July.
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Tahu started his career in rugby league with Newcastle, for whom he scored the winning try in the 2001 NRL grand final against Parramatta, also playing for Parramatta and Penrith before returning to the Knights.
He also played five Tests for the Kangaroos and 12 State or Origin games for NSW.
In between he fitted in two seasons of rugby union with the NSW Waratahs and played four Tests for the Wallabies in 2008-09.
