I'm doing research into Japanese internment, and I was reading about executive order 9095. This order created the Office of Alien Property Custodian (APC) as authorized by the Trading with the Enemy Act. I read that the APC was abolished by LBJ in 1966. But was this a permanent abolition of the ability to create the office, or does the Trading with the Enemy Act still allow the president to create this office?
The ability to create such an office derives (according to Roosevelt, who invoked the power), from the constitutional authority of the president and the Trading with the Enemy Act amended by the War Powers Act, 1941. A president cannot repeal a part of The Constitution or an act of Congress, but he can undo an act by a president (as long as Congress hasn't come along and taken back a power for example by changing the "authorized" part to "required"). In a sense, that office is permanently gone, but until Congress or SCOTUS change the law, another president could effectively re-create that office and even give it the same name. The appendix to Title 50 which authorized the office is still there (not repealed). It is remotely possible that some other act or court ruling effectively nullifies this part of the law, but that would have to be determined by some president attempting to re-create the office and then someone else suing to prevent it (based on such an effectively nullification).
The Office of Alien Property Custodian (APC) morphed into and became The Office of Foreign Assets Control (OFAC). The Treasury website as well as Wikipedia explain it.
Such an Office will always be necessary as long as the U.S. has "enemies"--an administrative more than a military term--and as long as Presidents declare or continue to maintain existing "national emergencies" which just about President has done since FDR. And some would argue going back even further than FDR.
"National Emergencies" are an ADMINISTRATIVE tool / remedy used administratively by the Executive to trigger certain additional administrative remedies, etc. Declaring a national emergency does NOT mean the nation is under literal physical attack or threat.
Hope that helps.