Why can a US court overturn a presidential executive order?

The executive order of the president of the United States is only an action order issued by the leader of the federal government-the president-to federal agencies (such as the Department of Immigration and Homeland Security-the unit that controls foreigners entering the United States), not a national law. This order cannot be ordered by the state government, but three States consider this order unconstitutional and report it to the federal court. According to the legal judgment, the federal judge considered the order unconstitutional, so he ordered to stop the execution of the order. The president can appeal to the superior court of the federal court-the circuit court (it seems that he also lost), or he can have the opportunity to appeal to the Supreme Court to finalize the case. China often said: Jun (the son of heaven) and Shu Ren are both guilty. Nor can it be unconstitutional.