DONALD TRUMP has not wasted time fulfiling campaign promises. In just his first week as America’s 45th president, Mr Trump signed executive orders and memoranda freezing federal hiring, backing out of the Trans-Pacific Partnership, defunding “sanctuary cities” that protect unauthorised immigrants, undermining Obamacare, restoring the “global gag rule” on abortion counselling, restarting the construction of two controversial oil pipelines through Native American lands, building a wall on the nation’s southern border, blocking Syrian refugees and residents of several majority-Muslim countries from immigrating to the United States and slashing regulations on businesses. These moves have provoked fierce criticism from Democrats and studied silence from most Republicans. What are executive orders, and what limits a president’s authority to issue them?

Only Congress can make laws; it is the executive branch’s duty to enforce them. Article II of the constitution specifies that presidents “shall take care that the laws be faithfully executed”, and they take an oath to do just that on inauguration day. But as John Locke pointed out in his “Second Treatise of Government,” gaps and ambiguities are hallmarks of written law. “[A] latitude”, Locke wrote, must be “left to the executive power, to do many things of choice which the laws do not prescribe”. When on January 25th he ordered the erection of a wall on the Mexican border, for example, Mr Trump claimed to be acting under the Immigration and Nationality Act and two other statutes. This move, he wrote, was designed to protect America’s “safety and territorial integrity” and to “ensure that the nation's immigration laws are faithfully executed”.

When a president’s executive order crosses into the realm of policymaking or violates the law, lawsuits pop up. Barack Obama’s 2014 decision to shield the parents of American citizens from deportation, for example, was halted by a federal district judge in Texas before it could get off the ground. (The Supreme Court later split 4-4 on whether Mr Obama’s order exceeded his authority, leaving the injunction in place.) Legislative officials sometimes rise in opposition, too. Pre-empting a rumoured order restoring the use of torture as an interrogation technique for suspected terrorists, John McCain, a Republican senator, said that Mr Trump “can sign whatever executive orders he likes. But the law is the law. We are not bringing back torture in the United States of America”. Other legislators will be keeping an eye on Mr Trump’s use of the presidential pen. In questioning Jeff Sessions, Mr Trump’s pick for attorney general, Ben Sasse, a Republican senator from Nebraska, noted his disdain for Barack Obama’s use of the privilege. Mr Sasse signalled that he would not countenance an imperial Trump presidency, either: the 44th president "exacerbated...political polarisation", he told Mr Sessions, "by saying he didn't have legal authority to do things and subsequently doing exactly those things"; it is a "crisis", he continued, "when kids don't understand the distinction between the legislative and executive branches".

Few presidents hesitate to put their executive power to quick use. Mr Obama issued fewer orders than most, averaging 35 a year (compared to Franklin Delano Roosevelt’s 307, the peak, and 36 and 46 for George W. Bush and Bill Clinton, respectively). But Mr Obama came out swinging, too, putting his name to 17 orders during the first month of his presidency. Not every signature bears fruit: Barack Obama ordered the closure of the Guantanamo Bay detention centre on January 22nd, 2009, a facility that still housed 41 inmates when he left office. The boldness of Mr Trump’s volley of orders in the opening days of his presidency may be similarly tempered, and the entry ban has already met with judicial resistance. Further court challenges are likely: threatening sanctuary cities with a loss of federal funding may violate the Tenth Amendment and the abortion gag rule runs up against the First.