A 12-match NRL ban will still hang over Ben Barba should he ever return to Australia if St Helens pursue – and succeed – in having his illicit drugs suspension overthrown so he can start his English Super League career immediately.

The NRL confirmed on Thursday it wouldn't allow Barba to return to action in the southern hemisphere without first serving his sentence for testing positive to cocaine after the Sharks' grand final celebrations last year as StHelens seek "final clarification" on his playing future.

Grounded: Ben Barba would be forced to miss 12 games if he returned to the NRL. Credit:Getty Images

Barba inked a deal at the English Super League powerhouse until the end of 2019 after exiting French rugby giants Toulon just months into a multimillion dollar deal.

The Rugby Football League and NRL have an unwritten agreement to honour suspensions incurred in either code should players switch between competitions, meaning Barba's St Helens bow might not be possible until August.