In September 2017, the Trump administration rescinded a planned Obama administration rule (that would've taken effect in March 2018) designed to increase pay transparency and diminish pay gaps. The rule required companies of a certain size to report how much they pay employees by race and gender.

In January 2017, Trump pulled the United States out of the Trans-Pacific Partnership (TPP), a 12-country trade deal designed to strengthen ties between the United States and East Asia. While the TPP had not yet been approved by Congress, it was considered a hallmark trade achievement of the Obama administration, which brokered the deal.

The DACA program, which Obama launched in 2012, offers undocumented immigrants who were brought to the United States as children the ability to live and work in the United States without fear of deportation. Trump announced he was ending the DACA program in September 2017, though the program has remained in place thus far amidst a host of ongoing lawsuits fighting its termination.

During Obama's presidency, the United States, along with 194 other countries, agreed to join the Paris Agreement, an international accord aimed at minimizing climate change and global warming. In June 2017, Trump announced that the United States was withdrawing from the agreement, citing economic concerns. Notably, the American withdrawal is not yet official, as UN rules mandate a multi-year withdrawal process.

In May 2018, Trump withdrew from the Iran nuclear deal, a 2015 agreement negotiated by Obama's administration. The multi-country deal lifted some economic sanctions on Iran in exchange for increased regulations on its nuclear program. As the New York Times reported, in announcing the United States' departure from the agreement, Trump called it "a horrible one-sided deal."

The proposed construction of the Keystone XL oil pipeline has been a subject of much controversy for many years. Dakota Access, along with several other companies, had sought to build an oil pipeline running through several states. The pipeline's construction prompted pushback from several groups, including Native Americans and environmentalists. In 2015, The Guardian reported that the Obama administration rejected a federal permit for construction of the pipeline, citing environmental concerns.

In 2017, Trump reversed this decision, with the Department of State citing job creation as one of the reasons for permit approval, as The Hill reported.

Back in October 2017, the Trump administration announced that it would allow almost any employer to claim a moral or religious exemption to Obamacare's birth control mandate, as Politico reported. The Trump administration issued two interim rules to allow for more flexibility with employer exemptions, making it far easier for companies to avoid providing employees with no-cost birth control than under Obama. These interim rules were finalized in November 2018.

However, just hours after the rules went into effect in January 2019, they were blocked nationwide by a federal court.

In May 2017, former Attorney General Jeff Sessions instructed federal prosecutors to "charge and pursue the most serious, readily provable offense" against defendants. This move marked a stark deviation from the policies of Obama's Justice Department. As NPR reported, former Attorney General Eric Holder had particularly instructed prosecutors to avoid charging nonviolent drug offenders with crimes that require mandatory minimum sentencing.

In October 2017, Trump's Department of Justice reversed an Obama-era policy that specified that transgender workers are protected from discrimination under the Civil Rights Act of 1964. At the time, BuzzFeed reported that Sessions argued that prohibitions on sex discrimination do not "encompass discrimination based on gender identity per se."

In September 2017, Trump's Secretary of Education Betsy DeVos rescinded Obama-era guidelines on investigating campus sexual assaults. DeVos' decision once again provided colleges with more flexibility in how they handle sexual assault cases, including through increasing the burden of proof necessary for determining whether a student is guilty of sexual assault. In November 2018, the New York Times reported DeVos released a draft of new guidelines that offer more protections to schools and to those who are accused of sexual assault.

In February 2017, the Trump administration ended Obama-era guidelines that mandated protections for transgender students in public schools. These protections included allowing students to use the bathrooms and locker rooms of their choice.

In 2015, President Obama issued an executive order banning the transfer of certain types of military-grade equipment to local police departments. In explaining his decision, the 44th president asserted (via CNN),

We've seen how militarized gear can sometimes give people a feeling like there's an occupying force as opposed to a force that's part of the community that's protecting them and serving them ... It can alienate and intimidate local residents and send the wrong message.

In August 2017, Trump signed his own executive order rescinding Obama's order. At the time, CNN reported that then-Attorney General Sessions told an audience of law enforcement officers:

The executive order the President will sign today will ensure that you can get the lifesaving gear that you need to do your job and send a strong message that we will not allow criminal activity, violence and lawlessness to become a new normal.

In March 2018, Trump signed a directive banning transgender individuals from serving in the military. Trump's directive stands in direct contrast to the Obama administration's 2016 announcement asserting that transgender individuals can serve openly in the U.S. military. Notably, Trump's transgender troop ban has faced several lawsuits since it was announced.

In April 2017, Trump officially ended an Obama-era program that offered temporary residency to undocumented children from several countries in Central America if they already had a parent legally residing in the United States. 2,714 minors had already been pre-approved for the program when Trump shut it down.

In January 2017, Trump re-instated and expanded what is known as the global gag rule, a policy that had been rescinded under President Obama. Trump's presidential memorandum mandated that all foreign organizations that receive U.S. global health assistance cannot provide abortion services or counsel patients about abortion. Trump's expansion of the global gag rule was perceived by reproductive health advocates as being particularly detrimental for women's and girl's health worldwide.

Under President Obama, the Department of Justice had planned to phase out its use of private prisons. As The Hill reported, on Aug. 16, 2016, an order from the department instructed officials not to renew any private prison contracts. In a memo announcing the change, then-Deputy Attorney General Sally Yates had written, "They simply do not provide the same level of correctional services, programs, and resources," as the Washington Post reported.

However, in February 2017, then-Attorney General Sessions rescinded this order.

As the New York Times reported in May 2017, Trump reversed over 20 Obama-era environmental regulations in the first 100 days of his administration alone. These rollbacks have continued throughout his presidency.

In December 2017, for example, Trump's administration overturned a 2015 Obama administration rule that limited fracking on public lands. And in March 2017, Trump ordered a re-valuation of Obama's Clean Power Plan, which sought to regulate greenhouse gas emissions from power plants. In August 2018, Trump released his own version of the plan, which Jennifer Lu of Popular Science characterized as "significantly more coal friendly."

On Dec. 11, the BBC reported that Trump's EPA released a proposal that wants to change the Obama administration's definition of federal waters. According to the outlet, the proposal could lift pollution restrictions on certain bodies of water.

On Dec. 8, Trump's Department of Agriculture announced that it is lowering nutrition standards for certain school lunch foods, the New York Times reported. These standards were implemented under the Obama administration — and largely spearheaded by former first lady Michelle Obama — as a way to improve students' health.

The new Trump administration rules relax grain requirements for school lunches, eliminating the Obama-era requirement that schools only serve "whole grain-rich" foods, the New York Times described. The Trump administration's rules also loosen restrictions on flavored milk and on salt content in food.

In June 2018, the Federal Communications Commission (FCC) repealed net neutrality regulations that were put in place under Obama. As the Washington Post reported, net neutrality ensured that internet service providers had to provide equal access to all internet content. Now that net neutrality has been repealed, internet service providers (ISPs) can legally choose to prioritize some internet content over others. This includes changing access speeds and selling paid access to certain content or download speeds, if ISPs so desire.

Back in April 2017, Trump signed a law allowing states to withhold federal family planning funding from organizations that perform abortions, including Planned Parenthood. As the New York Times reported, shortly before he left office, Obama implemented a rule prohibiting states from withholding family planning funding from organizations that happen to perform abortions in addition to other reproductive health services.

It's very apparent that Trump's administration has sought to dismantle key policy initiatives from Obama's time in office. It remains to be seen what, if any, other Obama-era initiatives Trump's administration will target — and how these potential changes may affect the United States.