It is believed that the prop has not asked for a release from the final five years of his deal, but the Eels and Panthers are discussing the potential of one.
His deal is worth over $4 million for the next five years, which is a big chunk of salary for a player currently used off the bench.
Campbell-Gillard has struggled to regain his best form after breaking his jaw against the Roosters halfway through last season, spending time in the Canterbury Cup throughout parts of 2019.
Penrith would reportedly be happy to pay for a portion of his salary elsewhere, but he has not yet been given permission to speak to rival clubs.
The Eels are currently in negotiations with Storm forward Christian Welch in a bid to boost their front-row stocks.