Swimmer Shayna Jack's two-year doping ban is being appealed by Sport Integrity Australia (SIA).

SIA on Monday lodged a statement of appeal with the Court of Arbitration for Sport (CAS), which suspended Jack for two years after she tested positive to the banned substance Ligandrol.

SIA chief executive David Sharpe says the appeal to CAS' appeals division is based on a need for clarity regarding anti-doping legal principles.

"Sport Integrity Australia will always act to ensure a level playing field for athletes," Sharpe said on Monday.

"In order to protect athletes and sporting competitions, we must have clarity and consistency in the application of the World Anti-Doping Code."

Sharpe declined to elaborate on the specifics of the appeal, citing confidentiality. A hearing date has not been set.

SIA was established in July this year, taking over management of the former Australian Sports Anti-Doping Authority among other agencies of the federal government.

Jack was initially banned for four years after testing positive to Ligandrol on June 26 last year, almost three weeks before the world swim titles in South Korea.

The 22-year-old Queenslander appealed her ban to CAS which early last month reduced her suspension to two years, finding Jack did not knowingly ingest the substance.

CAS on November 24 published its full decision in Jack's appeal, noting the swimmer suggested three possible sources for her positive test.

Jack told CAS one possibility was supplements she was taking were contaminated at manufacturing.

Another possibility was the supplements were contaminated by being prepared or mixed in a blender which may have been used by her partner or brothers which, in turn, might have been contaminated or have contained Ligandrol.

A third possibility was Jack may have come into contact with the Ligandrol or ingested it as a result of using pool and/or gym open to the public in Townsville or Cairns while training in May and June last year for the world championships.

CAS, in its ruling, said Jack "candidly admitted that she did not know how the prohibited substance came to be in her system".

"She offered the possibilities ... as the only possibilities she could think of," the CAS ruling said.

"There is simply no evidence ... that any of these speculative possibilities was in fact the reason for the presence of the prohibited substance in her system."

CAS' sole arbitrator for the appeal was Sydney QC Alan Sullivan, who described Jack as a wholly credible witness.

"She appeared to be completely straightforward, genuine and honest in the answers she gave," the CAS ruling said.

"Her dismay and upset at the situation she found herself was evident.

"The applicant (Jack) did not come across ... as someone who would intentionally cheat by deliberately taking a prohibited substance."