There was an EO, but that is not law. Cannabis is still schedule I last I checked. The order is to make it schedule III.
A president can not make a law, only sign them into existence. He can also direct enforcement or lessen it.
As far as I understand, the Schedule of Cannabis is written into the US Code. So Congress would need to amend it.
https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim...
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