The Poolbeg Incinerator project has been cleared of breaching EU rules on state aid.
The European Commission ruled that the project will be carried out on market terms and does not involve state aid.
But the project is still facing a ruling on another complaint concerning public procurement procedures which is ongoing.
Dublin City Council's manager Owen Keegan has said that the project will be cancelled if either of the complaints go against the council.
The council is involved in a public private partnership with the company Covanta and stands to lose over €90 million if the plan is cancelled.
These costs would be repaid by Covanta if it does go ahead.
The plan for an incinerator processing 600,000 tonnes of waste is opposed by local residents, a majority of city councillors and other waste companies.