As he prepares to leave office in three weeks, President Obama is still trying to shape his legacy. On Dec. 20 the White House announced the withdrawal of millions of acres of Atlantic and Arctic territory from petroleum development. This week Mr. Obama proclaimed 1.35 million acres in Utah and 300,000 acres in Nevada to be new national monuments. But all the soon-to-be ex-president will prove is the fleeting nature of executive power.

These actions, like many others he has taken, are vulnerable to reversal by President-elect...