(CNN) - With the flick of a pen, a new president can undo years of work by a previous administration through his constitutional executive powers.
President Donald Trump has signed a number of executive actions, including executive orders and presidential memorandums, aimed both at fulfilling his campaign promises and at rolling back the policies of former President Barack Obama.
"We do not need new laws," Trump said January 25, soon after signing two executive orders related to immigration, indicating he'll test the existing framework.
Here's a look at both the orders and memorandums he has signed so far:
Trump's executive orders
An executive order is a legally binding document that declares government policy. Unable to reverse a law passed by Congress, it is more often used to delegate and direct government agencies and departments.
Since taking the inaugural oath, Trump has signed 12 executive orders.
Day 1: Minimizing the Economic Burden of the Patient Protection and Affordable Care Act Pending Repeal
Hours after taking the oath of office, Trump issued an executive order aimed at rolling back Obamacare. The directive called on the secretary of health and human services, in addition to other agencies, to interpret regulations as loosely as possible to minimize the financial burden on individuals, insurers, health care providers and others.
Who will it affect? The order's language is somewhat vague, and considering that Obamacare was passed through Congress, this presidential action can't change the law. The process of changing the law is underway, however. The House of Representatives recently approved a budget that would allow Congress to repeal parts of the Affordable Care Act, and congressional Republicans and the White House are scrambling to develop a replacement. Trump hopes to replace it with his own administration's health care law. All of that means this executive order's implications are unknown.
Day 4: Expediting Environmental Reviews and Approvals for High-Profile Infrastructure Projects
Trump directed those in charge of evaluating the environmental impact of infrastructure projects to return their assessments in a timelier manner.
Who will it affect? Trump promised to make new spending on infrastructure projects a priority of his administration. He needs Congress to approve any new spending bill, but this order could help expedite certain projects.
Day 6: Border Security and Immigration Enforcement Improvements
Fulfilling another of his campaign promises, Trump instructed the Department of Homeland Security to commence immediate construction of a 1,900-mile long wall along the southern border with Mexico, using existing federal funds to get it started. The directive also signaled beefing up the border with an additional 5,000 border protection officers.
Who will it affect? It's unclear where the funds for building the wall will come from. Congress would need to approve any new funding for both the wall. Some of the land is privately owned, which could prove another hurdle. But it could potentially bring more jobs and a financial injection to the economy of the border regions once construction begins and with the introduction of more border agents. More officers would also probably mean more deportations of undocumented immigrants.
Day 6: Enhancing Public Safety in the Interior of the United States
This executive order aims to tackle the issue of undocumented immigrants through deportation and tripling resources for enforcement with 10,000 additional immigration officers. It also targets so-called "sanctuary cities" -- municipalities, states and other entities which can refuse to turn over undocumented immigrants to federal authorities through a variety of shielding policies -- by withholding funding.
Who will it affect? Again, this order would likely see an increase in the number of undocumented immigrants being deported. And while the administration can't cut off all federal funding, as Congress pays out much of it, the President could put pressure on cities to comply.
Day 7: Protecting the Nation From Foreign Terrorist Entry into the United States
This executive order prevents refugees from entering the country for 120 days and immigrants from seven Muslim-majority nations out for three months.
Who will it affect? The countries directly affected are Iran, Iraq, Syria, Sudan, Libya, Yemen and Somalia. This is the "extreme vetting" Trump promised during the campaign, but caught the world by surprise. It set off widespread chaos and confusion at airports and for agencies tasked with implementing it. A federal appellate court upheld a trial court ruling temporarily blocking Trump's travel ban.
Day 9: Ethics Commitments by Executive Branch Appointees
Designed to give teeth to Trump's campaign pledge to "drain the swamp" in Washington, the order imposes a lifetime ban on administration officials lobbying for foreign governments, and a five-year ban for other lobbying. Officials also have to pledge they "will not for a period of 2 years from the date of my appointment participate in any particular matter involving specific parties that is directly and substantially related to my former employer or former clients, including regulations and contracts."
Who will it affect? Some cabinet picks will likely have to submit new ethics agreements if they have financial ties with companies affected by the actions of their departments. They will now have to agree to a two-year moratorium, instead of the original one year.
Day 11: Reducing Regulation and Controlling Regulatory Costs
According to the order, when a new regulation is disseminated, at least two existing regulations should be identified for removal "and that the cost of planned regulations be prudently managed and controlled through a budgeting process." It says that for fiscal year 2017, "the total incremental cost of all new regulations, including repealed regulations, to be finalized this year shall be no greater than zero."
Who will it affect? This order immediately affects the administration's departments and agencies. However, Trump says it will help small businesses get back on track by reducing the number of regulatory hurdles a start-up has to jump to get off the ground.
Day 15: Core Principles for Regulating the United States Financial System
This executive order was widely portrayed as Trump's rollback of the Dodd-Frank Act, the Wall Street reform law enacted in 2010 in response to the financial crisis. In reality the order lays out a new set of "core principles" that the treasury secretary and the Financial Stability Oversight Council must use to review existing laws and regulations.
Who will it affect? At the surface, it is purely a directive for regulatory agencies to consider Trump's set of priorities and return a report within 120 days on which current laws don't abide by the order and the actions that may need to be taken.
Day 18: Task Force on Crime Reduction and Public Safety
Trump outlines a commitment to reducing the US crime rate by tackling illegal immigration, drug trafficking and violent crime. It directs Attorney General Jeff Sessions to establish a task force that will collaborate with law enforcement nationwide and design new strategies to reduce crime.
Who will it affect? Speaking to the press shortly after signing the order, Trump said, "I'm directing (the) Department of Justice and the Department of Homeland Security to undertake all necessary and lawful action to break the back of the criminal cartels that have spread across our nation and are destroying the blood of our youth and other people."
Day 18: Enforcing Federal Law with Respect to Transnational Criminal Organizations and Preventing International Trafficking
In his bid to tackle crime, Trump also signed an order targeting transnational drug cartels and called for agencies to increase intelligence sharing and submit a report on progress within four months.
Who will it affect? Initially, this order remains focused on agencies and departments, but their actions could lead to new strategies for a crackdown on drugs, considering it calls for progress reports.
Day 18: Preventing Violence Against Federal, State, Tribal, and Local Enforcement Officers
A further order on crime directed the Justice Department to use existing federal law to pursue individuals who carry out crimes against law enforcement officers.
Who will it affect? Again, the order directly affects those working for Justice Department and the divisions it oversees. Any policy or strategy changes could lead to more prosecutions.
Day 20: Providing an Order of Succession Within the Department of Justice
This order designates who will serve as acting attorney general -- and in which order -- in the event that the current attorney general dies, resigns or is unable to perform his normal functions and duties. Trump named his preferences in the following order: US attorney for the Eastern District of Virginia, US attorney for the Northern District of Illinois and US attorney for the Western District of Missouri.
Who will it affect? In the event that Sessions, the new attorney general, is unable to fulfill his normal duties, Trump's succession pick, Dana Boente, US attorney for the Eastern District of Virginia, will be prepped to fill the gap. Boente briefly acted as attorney general after Trump fired the former acting head, Sally Yates, after she declined to defend the administration's executive action on immigration.
Trump's presidential memorandums
In addition to executive orders, Trump has signed 12 presidential memorandums, which have less legal weight than an executive order and are more important as documents laying out the priorities of his administration. They can have real consequences, however.
1. Memorandum for the Heads of Executive Departments and Agencies -- An order to halt any new federal regulations until they can be reviewed by the new administration. Actually rolling back regulations the Obama administration put in place will take time and a bureaucratic process. This was a near exact replica of executive orders that the past two presidents have had their chiefs of staff issue at the beginning of their administrations.
2. Regarding the Mexico City Policy -- Reinstates a policy that, among other things, restricts US funding to nongovernmental organizations that provide abortions.
3. Regarding Withdrawal of the United States from the Trans-Pacific Partnership Negotiations and Agreement -- Withdraws the United States from a massive trade deal that was negotiated by the Obama administration, but not yet ratified by Congress. It was largely a symbolic move since the TPP was never officially enacted.
4. Regarding the Hiring Freeze -- Institutes a freeze on the hiring of new federal workers, except for the military. It contains wide exemptions for jobs "necessary to meet national security or public safety responsibilities," which is a broad definition. It also exempts military hiring, which accounts for a third of federal jobs.
5. Construction of American Pipelines - Says new pipelines should be made using US-produced materials.
6. Regarding Construction of the Keystone XL Pipeline -- Kick starts a pipeline the Obama administration had quashed. Trump's order allows the pipelines to proceed but the projects are still a long way from getting underway. Trump himself said the US would renegotiate the terms of the pipelines, which implies a lengthy process with several competing interests.
7. Regarding Construction of the Dakota Access Pipeline -- Prioritizes a controversial pipeline that was the subject of protests in North Dakota
8. Streamlining Permitting and Reducing Regulatory Burdens for Domestic Manufacturing -- Requests a plan to make the permitting process easier for US manufacturers.
9. Rebuilding the US Armed Forces -- spurs military spending and directs Defense Secretary James Mattis to begin "developing a plan for new planes, new ships, new resources and new tools for our men and women in uniform."
10: Plan to Defeat the Islamic State in Iraq and Syria -- Trump orders a new plan to defeat ISIS to be drawn up within 30 days. It will include mechanisms to cut off all of the terror group's funding, including sale of oil and historical artifacts.
11: Organization of the National Security Council and the Homeland Security Council -- Elevates the President's chief strategist, Stephen Bannon, to full membership of the NSC and downgrades the roles of director of national intelligence and the chairman of the Joint Chiefs of Staff who "shall attend where issues pertaining to their responsibilities and expertise are to be discussed."
12: Presidential Memorandum on Fiduciary Duty Rule -- It's an apparent response to Obama's 2016 Fiduciary Rule, which prohibited retirement advisers from accepting incentives for promoting a particular fund over others. Trump's presidential memo calls for the Labor Department to review the rule.
One week in: Who signed more -- Trump or Obama?
Trump is the latest in a long line of incoming commanders in chief flexing their executive muscles the first week on the job. Presidents, going all the way back to George Washington, have often taken unilateral steps to skirt past adverse lawmakers and bypass Congress -- some more than others.
Getting straight to business on Inauguration Day, Trump immediately signed an order instructing federal agencies to weaken Obamacare. Not since Bill Clinton in 1993 had an incoming president signed an executive order on his first day in office.
Trump can reverse any of his predecessor's executive orders, just as his successor can overturn anything the 45th President signs while in office.
Both Trump and Obama signed five executive orders within their first seven days in office.
Shortly after his inauguration, Obama signed executive actions aimed at closing the detention camp at Guantanamo Bay, Cuba, and shuttering secret detention facilities -- promises he had assured voters of while on the campaign trail.
He signed six executive orders in the first 30 days of his first term that reversed eight orders from George W. Bush.
Unlike executive orders, presidential memos do not have to be released publicly so it is hard to document the exact number issued during a president's term.
Obama was known for using alternative presidential actions more often than executive orders.
With several more expected executive orders and Trump also eyeing one on voter fraud, one thing is clear: Like many of his predecessors, the President is trying to use his executive powers to make his campaign promises a reality.