The news has been revealed in a Yorkshire Post report.
Randall has previously represented the England Cricket Board and the FA Premier League, and also counts soccer star Wayne Rooney amongst his clients.
Solomona is currently the subject of bid to sign him by rugby union outfit Sale Sharks.
The situation has become complicated by Sale’s reluctance to pay the £300,000 price tag attached to the prolific winger by the Tigers.
Solomona did not return to preseason training earlier this month, and was seen at Sale’s training ground.
Castleford insist that the player was never for sale, but the RU club is now reportedly claiming that Solomona has retired from rugby league, and is now beginning a new career in a different sport.
The Tigers have enlisted Randall to help them fight that claim in court, along with Richard Cramer, from Leeds-based Front Row Legal sports solicitors.
The report also asserts that two other clubs were interested in Solomona, one Super League outfit and another union club.
Solomona’s agent is Andy Clarke, brother of Sky Sports pundit and former Wigan player Phil Clarke.