Dow Jones newswires reported on Thursday that a spokesman said this would now explicitly be the case.
The news comes after widespread criticism from industry observers and the German government over reports that GM had promised all patents to the US government as collateral in return for a bailout.
The GM spokesman would not comment on those reports, but offered assurances that all patents were held by the US-based subsidiary Global Technology Organisation.
He said that any new Opel owner would have full access to these rights.
A buyer for Opel and its British arm Vauxhall has still not be found, although this week European Opel dealers said they were working to find a way to buy up to 20 percent of the company over the next three years.
However, this has not been greeted by experts, who say the time needed to raise the money is far too long.