As past and present Cronulla players brace for their imminent day of reckoning, a four-day hearing starting at Sydney's Administrative Appeals Tribunal on Tuesday shapes as crucial to the future of the former Penrith and Canberra winger.

After almost a year in exile Earl and his lawyer Tim Unsworth are endeavouring to have overturned the player's entering into ASADA's register of findings by the agency's independent review body, the Anti-Doping Rule Violation Panel.

The 24-year-old's hearing in the AAT is listed to begin on Tuesday before Deputy President Stephen Frost, and is scheduled to last four days.

It will take place behind closed doors, and not open to the public or media, but Earl is hoping its outcome later this week could clear the way for him to make a return to the NRL rather than continue to sit out a lengthy ban.

As it stands he faces a possible four-year suspension over more than 30 anti-doping violations levelled at him relating to his time at the Panthers in 2011 and the Raiders in 2012 and 2013.

However, Earl could potentially have ASADA's allegations against him thrown out if his team can successfully argue in the AAT that text messages found on his phone were unlawfully obtained and disseminated by Customs officials at Sydney Airport.

The messages are understood to form a central plank of the case against the three-quarter and questions are expected to be asked in the AAT about whether it was legal for them to be taken from his seized phone when he returned home from Thailand in January last year and then to be passed on ultimately to ASADA.

Earl has previously noted the role the text messages played in convincing him to make admissions to ASADA investigators last August, and railed against the process by which he was then provisionally suspended by the NRL two days later, believing he was cornered into standing down.

Unsworth has also been adamant that the NRL breached sections 4.19 and 4.20 of the National Anti-Doping scheme, telling Fairfax Media in June that by announcing last August Earl had admitted using and trafficking the peptide CJC-1295 before he was placed on the register of findings the game's governing body had neglected an obligation to keep the matter confidential.

Earl's name was eventually entered into the register by the ADRVP in early June, triggering the NRL to schedule an appearance before their anti-doping tribunal later that month.

That was postponed when the player successfully won an injunction in the AAT, but if he fails in his appeal the panel chaired by former High Court judge Ian Callinan QC will quickly be reconvened to determine a penalty.

As for the doping claims facing Earl, a charge of trafficking CJC-1295 was dropped by ASADA but NRL chief operating officer Jim Doyle in June outlined a range of alleged violations including the injecting of that peptide while he was recovering from shoulder surgery at the Panthers and the trafficking and attempted trafficking of other prohibited substances..

They include growth hormone Somatropin, selective androgen receptor modulators (SARMS), anabolic agent Clenbuterol and testosterone blend Sustanon.