What Donald Trump can and can't do on his first day in office

It sounds like President-elect Donald Trump is going to have quite the busy day on Jan. 21. Judging by Trump's video message on Nov. 21, his October 2016 "Contract with the American voter" and the pledges he made while campaigning, Donald Trump's first full day in the Oval Office is currently set to include everything from starting the process of removing millions of undocumented immigrants to learning the difference between Hezbollah and Hamas.

But how much will he actually be able to accomplish on that one fateful day? His exact actions remain to be seen, but here's what we know Trump can and cannot accomplish right away.

What Trump can't do

Though Trump's position as president clearly gives him a lot of power, the existence of Congress means that, in many cases, Trump's immediate authority can only go so far. He cannot, for instance, repeal the Affordable Care Act, which would require congressional action — and, with the Republicans not having a clear enough majority to overcome a Democratic filibuster, a complete repeal of the law seems unlikely, though significant changes are possible.

Despite Trump's climate change doubting, he also can't immediately withdraw from the Paris climate change agreement, which contains a clause that countries must wait three years from when the treaty takes effect to pull out, nor can he dismantle existing Environmental Protection Agency regulations without the approval of Congress. Additionally, the New York Times notes, any attempt by Trump to dismantle the regulations set by the Obama administration on Arctic offshore drilling will likely be met with a lengthy legal battle.

One of the other pledges Trump has made for his first day in office is to begin to impose term limits on elected officials in Congress and impose a five-year ban on government employees in Congress and the White House switching to lobbying roles. NPR notes, however, that any proposal for term limits would require a constitutional amendment, and the president has no constitutional role in that process. Congressional leaders are also not on board, with Sen. Mitch McConnell saying, "I would say we have term limits now — they're called elections." Congress is also unlikely to get on board with the lobbying restrictions, with many seeing high-paying lobbying jobs as a reward for their public service, according to NPR.

Trump's presidential promises have also been tough on trade — particularly with China — but his powers to enact tariffs on international businesses and countries are still still limited. The New York Times explains that tariffs require congressional approval, and though Trump has promised to call up business executives and threaten to impose tariffs if they move jobs overseas, tariffs against specific companies are banned in the Constitution. 

Trump does have the power to retaliate by imposing "safeguard" [first vox link] tariffs against specific imports. Vox reported this could be done in an instance where the president determines an American industry is in "serious, immediate danger" because of competition from international imports and needs relief.

Of course, one of Trump's central issues from the time he announced his candidacy has been immigration, and while there's a lot he will be able to do on day one, there are some things that won't be possible. Though Trump does have the power to deport undocumented immigrants who have been convicted of a crime without congressional approval, NPR notes, the actual logistics of beginning to deport this many immigrants are likely too daunting (particularly on day one). Vox reports that under the current immigration budget, the maximum number of illegal immigrants deported would be about 510,000 per year — only 100,000 more than the most deported in a year by President Barack Obama. Any sort of budgetary increase to allow for more deportations would likely be a process going far beyond Trump's first day.

What Trump can do

For all the limitations he has, though, there's a lot Trump can get done on his first day. Upon assuming the presidency, Trump will have the power to undo Obama's 32 executive orders, which include everything from allowing federal funding for international health groups who perform abortions to restrictions on the government's greenhouse gas emissions.

"Trump spends several hours signing papers — and erases the Obama presidency," a Republican close to Trump's campaign told the New Yorker in September.

One of the primary mandates that Trump can easily repeal is the Deferred Action for Childhood Arrivals, which has temporarily authorized some 700,00 people who moved to the U.S. without documentation as children to remain in the country and be protected from deportation. By rescinding the law, Trump now has the ability to begin deporting these people, who have provided their information to the government through the program. 

Another way Trump can make the country unsafe for undocumented people on his first day is by cutting off federal funding to "sanctuary cities," municipalities in the U.S. that don't actively prosecute undocumented immigrants.

When it comes to fighting immigration from outside of the U.S., Trump will have even more power. Though his infamous proposed ban on all Muslims entering the U.S. is legally dubious, he can ban all immigrants coming from certain countries, using Section 212(f) of the Immigration and Nationality Act, which, as quoted in the Detroit Free Press, states, "Whenever the president finds that the entry of any aliens or of any class of aliens into the United States would be detrimental to the interests of the United States," the president can prevent them from entering legally for "such period as he shall deem necessary." 

Trump, Vox notes, also has the power to order the Department of Homeland Security to slow or freeze the issuance of green cards, as well as stop issuing specific classes of visas — such as H-1B visas, which Trump has long criticized. 

Additionally, Trump can also instruct the State Department to stop issuing visas for citizens of the 23 "recalcitrant" countries that don't accept entry of their own citizens who were deported from the U.S. because they were convicted of a crime, NPR reported. These countries include Afghanistan, Cuba, Iran and Zimbabwe.

While, as mentioned previously, Trump's first-day tariff powers are limited, he does have the power to label China a "currency manipulator" — though, the BBC notes, beyond annoying China, this labeling probably won't have much impact. More significantly for trade, Trump will have the power on his first day to begin the process of withdrawing from NAFTA. CNN Money reports that under Article 2205 of the agreement, which Trump has cited in speeches, a country can withdraw from the agreement six months after providing written notice, which Trump can do without Congress *(though some experts disagree about this). Since the U.S. has not removed itself from a trade deal since 1866, however, it's hard to know what would happen next.

Trump's first day in office could also bring about a swift end to this week's victory for the Dakota Access pipeline protesters. Trump will be able to authorize construction on both the Dakota pipeline and the Keystone XL pipeline — which is likely to happen, considering that Trump has reportedly invested in the companies behind both.

Other things that are well within the realm of possibility for Trump's first day include beginning the process of appointing a new Supreme Court justice and dismantling the Iran nuclear agreement, which Vox reports could be done by issuing an executive order that re-imposes U.S. economic sanctions that were lifted as part of the deal. Trump has also said that he will call a meeting with military personnel on his first day in office, in which he will give them 30 days to formulate a plan to defeat ISIS.

And if all that isn't power isn't enough, there's one more thing that Trump has unfettered access to on day one: the nuclear codes.