The Australian government announced legislation last month after an investigation it said showed the tech giants held too much market power in the media industry, a situation it said posed a potential threat to a well-functioning democracy.
Under the code, Google and Facebook will be subject to mandatory price arbitration if a commercial agreement on payment for Australian media cannot be reached.
"This bargaining code is a journey, if we see market power elsewhere, we can add them to the code," Australian Competition and Consumer Commission Chairman (ACCC) Rod Sims said in an interview aired during the Reuters Next virtual event on Tuesday.
Digital platforms face fines of up to A$10 million (US$7.7 million) if they do not comply with the decision.
Sims said the regulatory code was the best approach to ensure a level playing field, noting that competition laws around the world had failed to stop Facebook and Google gaining significant market power.
The Australian law, which has broad political support and is expected to be voted on in parliament early this year, was formulated after an ACCC inquiry that found for every A$100 of online advertising spend, $53 goes to Google, $28 to Facebook and A$19 to other media companies.