Spiers, who last played for League One side Midlands Hurricanes, took a drugs test during a training session in May 2022 which showed traces of boldenone - an anabolic steroid.
The 31-year-old was charged for the use of a prohibited substance in November last year which he admitted to and is now suspended from competitive action until August 2025.
Jane Rumble, chief of UK Anti-Doping, said: "Boldenone is an anabolic steroid that can increase an athlete's muscle mass, enhancing their performance.
"There is no place for anabolic steroids in sport, and there are serious consequences for athletes caught taking them."
Formerly of Wakefield Trinity, Doncaster and York City Knights, Spiers will be allowed to resume training in June 2025, two months before his ban comes to an end.
