The Environmental Protection Agency failed to stop shipments of uranium ore stopping at ports last year when an Australian company breached legal requirements.
According to details obtained under the Official Information Act, Energy Resources of Australia should have provided a contingency plan in case of a uranium ore spill.
But instead of terminating the approval, the agency removed that obligation.
In April, EPA chief executive Rob Forlong said it would change the rules so there is no longer a legal requirement to stop a ship's access to port when controls are breached.
The agency says the company provided a contingency plan when requested, and no action was taken.
It says uranium ore presents a low risk to human health.