The Waratahs did not release any details about the alleged breach but the 31-year-old's manager Greg Keenan said in a statement released to The Sunday Telegraph that Sailor had provided a positive sample to a drugs test.
"Wendell Sailor has been notified by the Australian Sports Anti-Doping Authority that part A of a sample he provided recently has returned positive to a banned substance," said Keenan.
"The ARU has also been notified by the agency, and the ARU and NSWRU have consequently stood Wendell down from playing duties.
"We have approached the Rugby Union Players' Association to request legal advice. At this stage, Wendell has no comment to make."