The President of the United States issued an order to block the acquisition of United States Steel Corporation by Nippon Steel Corporation due to concerns about national security. The order states that the companies involved must fully abandon this acquisition within 30 days unless an extension is granted by the Committee on Foreign Investment in the United States (CFIUS). The companies must regularly report their compliance and efforts to abandon the merger to CFIUS. The President reserved the authority to issue further orders if necessary to protect national security.
Simple Explanation
The President said that a big company from another country can't buy a big American steel company because it might not be safe for the country. They have to stop trying to buy it in 30 days unless they get more time to do so.