PHOTO: Photo Illustration: Getty Images/CNNMoney
Now playing
00:40
Trump signs Russia sanctions bill
President Donald Trump addresses the 73rd session of the United Nations General Assembly, at U.N. headquarters, Tuesday, Sept. 25, 2018. (AP Photo/Richard Drew)
President Donald Trump addresses the 73rd session of the United Nations General Assembly, at U.N. headquarters, Tuesday, Sept. 25, 2018. (AP Photo/Richard Drew)
PHOTO: Richard Drew/AP
Now playing
02:17
Trump claim to world leaders met with laughter
Trump laughing with me
Trump laughing with me
PHOTO: CNN
Now playing
01:38
Trump: World leaders were laughing with me
PHOTO: CNN Illustration/Getty Images
Now playing
01:59
Trump warns about doing business with Iran
President Donald Trump talks on the phone aboard Air Force One during a flight to Philadelphia, Pennsylvania, to address a joint gathering of House and Senate Republicans, Thursday, January 26, 2017. This was the Presidentâs first Trip aboard Air Force One. (Official White House Photo by Shealah Craighead)
President Donald Trump talks on the phone aboard Air Force One during a flight to Philadelphia, Pennsylvania, to address a joint gathering of House and Senate Republicans, Thursday, January 26, 2017. This was the Presidentâs first Trip aboard Air Force One. (Official White House Photo by Shealah Craighead)
PHOTO: Shealah Craighead/White House Photo/Getty Images
Now playing
01:36
WH stops summarizing calls with world leaders
PHOTO: CNN
Now playing
01:32
Clarke: Trump diminishes US role and influence
US President Donald Trump and Russia
US President Donald Trump and Russia's President Vladimir Putin attend a joint press conference after a meeting at the Presidential Palace in Helsinki, on July 16, 2018. (Photo by Brendan SMIALOWSKI / AFP) (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
PHOTO: BRENDAN SMIALOWSKI/AFP/Getty Images
Now playing
01:59
Trump: We are all to blame for Russia relations
SAN FRANCISCO, CA - FEBRUARY 08:  Canada Prime Minister Justin Trudeau looks on before speaking to members of the media during a visit to AppDirect on February 8, 2018 in San Francisco, California. Trudeau is visiting several cities in the U.S.  (Photo by Justin Sullivan/Getty Images)
SAN FRANCISCO, CA - FEBRUARY 08: Canada Prime Minister Justin Trudeau looks on before speaking to members of the media during a visit to AppDirect on February 8, 2018 in San Francisco, California. Trudeau is visiting several cities in the U.S. (Photo by Justin Sullivan/Getty Images)
PHOTO: Justin Sullivan/Getty Images North America/Getty Images
Now playing
00:57
WaPo: Trump admits he gave Trudeau false info
US President Donald Trump and French President Emmanuel Macron hold a joint press conference at the White House in Washington, DC, on April 24, 2018. (Photo by LUDOVIC MARIN / AFP)        (Photo credit should read LUDOVIC MARIN/AFP/Getty Images)
US President Donald Trump and French President Emmanuel Macron hold a joint press conference at the White House in Washington, DC, on April 24, 2018. (Photo by LUDOVIC MARIN / AFP) (Photo credit should read LUDOVIC MARIN/AFP/Getty Images)
PHOTO: LUDOVIC MARIN/AFP/Getty Images
Now playing
00:44
Trump has 'terrible' phone call with Macron
PHOTO: photo illustration: getty images/shutterstock/cnnmoney
Now playing
01:17
WH confirms Trump, Putin discussed meeting
travel ban trump then and now orig nws_00002328.jpg
travel ban trump then and now orig nws_00002328.jpg
Now playing
01:23
Trump's travel ban then and now
PHOTO: ABC News
Now playing
01:01
Trump touts trust with Kim in TV interview
PHOTO: Kevin Lim/THE STRAITS TIMES
Now playing
02:11
Memorable moments from the Singapore summit
TOPSHOT - A vendor picks up a 100 yuan note above a newspaper featuring a photo of US president-elect Donald Trump, at a news stand in Beijing on November 10, 2016.
The world
TOPSHOT - A vendor picks up a 100 yuan note above a newspaper featuring a photo of US president-elect Donald Trump, at a news stand in Beijing on November 10, 2016. The world's second-largest economy is US president-elect Donald Trump's designated bogeyman, threatening it on the campaign trail with tariffs for stealing American jobs, but analysts say US protectionism could create opportunities for Beijing. / AFP / GREG BAKER (Photo credit should read GREG BAKER/AFP/Getty Images)
PHOTO: GREG BAKER/AFP/AFP/Getty Images
Now playing
01:48
US trade with China, explained
PHOTO: CNN
Now playing
01:07
Trump announces withdrawal from Iran deal
US President Donald J. Trump delivers his first address to a joint session of Congress from the floor of the House of Representatives in Washington, DC, USA, 28 February 2017.   / AFP / EPA POOL / JIM LO SCALZO        (Photo credit should read JIM LO SCALZO/AFP/Getty Images)
US President Donald J. Trump delivers his first address to a joint session of Congress from the floor of the House of Representatives in Washington, DC, USA, 28 February 2017. / AFP / EPA POOL / JIM LO SCALZO (Photo credit should read JIM LO SCALZO/AFP/Getty Images)
PHOTO: JIM LO SCALZO/AFP/Getty Images
Now playing
01:46
Trump's foreign policy: One thing to know
(CNN) —  

US President Donald Trump signed into law new sanctions against Russia, Iran and North Korea on Wednesday, but he had little choice in the matter.

Members of Congress supported the legislation in such overwhelming numbers that they had the power to override the President if he vetoed the legislation, which he described as “seriously flawed.”

Here’s what you need to know:

Russia sanctions

Why now?

Congress justified a new set of sanctions against Russia – and the refinement of existing ones – because of Moscow’s interference in the 2016 US election, its human rights abuses and its military aggression in Ukraine, including the annexation of Crimea.

Who’s targeted?

The Russian sanctions will target people and entities that:

undermine US cybersecurity on behalf of the Russia government

invest certain amounts in Russia’s energy export pipelines

conduct “significant” transactions with Russian defense and intelligence agencies (though this will come into effect six months from now)

commit, or assist in, serious human rights abuses

commit acts of “significant” corruption

provide support to the Syrian government to acquire arms

invest, or facilitate the investment of, $10 million or more in the Russian government’s privatization of state-owned assets in a 12-month period that could “unjustly” benefit government officials or their associates.

What are the sanctions?

The law includes a list of sanctions, which include freezing assets, such as property, revoking US visas and banning exports from the United States to sanctioned people or entities. In certain cases, the President must impose at least five types of sanctions on a person or entity.

What’s the fallout?

For Russia, the new law limits the US President’s power to unilaterally ease or waive most sanctions without the approval of Congress. This shift of power is central to Trump’s resentment for this law, he indicated on Wednesday, arguing that the law encroached on the executive’s authority. The President claimed after signing the bill into law that he could “make far better deals with foreign countries than Congress.”

The White House said in a statement that the law includes “a number of clearly unconstitutional provisions” that “purport to displace the President’s exclusive constitutional authority to recognize foreign governments, including their territorial bounds.”

The new law has all but crushed hopes of the reset in US-Russia relations that both Trump and Putin had openly called for. Moscow retaliated after the bill passed Congress, ordering the US to cut staff at its diplomatic mission by 755 people.

Russian Prime Minister Dmitry Medvedev also said the sanctions showed a “fully-fledged trade war” had been declared against Russia and that “the Trump administration demonstrated complete impotence, in the most humiliating manner, transferring executive powers to Congress.”

Iran sanctions

Why now?

US officials say that Iran has continued to test and develop ballistic missiles, in what Washington and its European allies say are in violation of a UN Security Council Resolution. As recently as July, the US State Department criticized Iran for continuing to develop its ballistic missile program, but did not give details of when or how they did so.

US officials have also accused Iran of supporting groups that Washington has designated as terrorist organizations, such as Hezbollah and Hamas, and violent groups, including the Palestinian Islamic Jihad, arguing the country is threatening to destabilize the Middle East.

In mid-July, the Trump administration sanctioned 18 people and entities, under existing laws, for non-nuclear reasons, such as supporting ballistic missile development.

The US State Department at the time accused Iran of propping up the regime of Syrian President Bashar al-Assad “despite Assad’s atrocities against his own people” and arming Houthi rebels in Yemen.

Who’s targeted?

The sanctions center around the country’s ballistic missile program, human rights abuses and the Islamic Revolutionary Guard Corps (IRGC). The IRGC, which is sanctioned under other laws, has been slapped with terrorism-related sanctions for the first time and is essentially now blacklisted by the US.

The new law says the IRGC is behind Iran’s international destabilization program, including international terrorism and the ballistic missile program.

The law directs the President to impose sanctions on people or entities that:

are members of the IRGC and foreign persons that are officials, agents, or affiliates of the IRGC

knowingly engage in activity that contributes to or facilitates the ballistic missile or weapons of mass destruction programs. This includes anyone who manufactures, transfers or even transports these capabilities.

are serious human rights abusers, including those responsible for extrajudicial killings and torture. It also includes gross violations of international human rights against people who seek to expose illegal government activity, or those trying to obtain or promote international human rights. Sanctions can be applied to anyone supporting such abuses.

contribute to the supply, sale or transfer of certain weapons to or from Iran. These include battle tanks, armored combat vehicles, combat aircraft, warships and missiles, among others. Those contributing financial assistance or services related to these weapons can also be sanctioned.

What are the sanctions?

The sanctions include the blocking of property, exclusion from entering the United States and the freezing of transactions with people subject to sanctions.

What’s the fallout?

Iranian officials have accused the United States of using the sanctions to undermine the Iran nuclear deal.

The landmark 2015 nuclear deal signed by the United States, three European powers, Russia and China obliged Iran to scale back its nuclear program in return for an easing of sanctions.

President Trump has long criticized the agreement and vowed to pull the country out of it during his election campaign.

Iranian Foreign Ministry spokesman Bahram Qasemi warned that the “hostile” US measures would impact the implementation of the nuclear deal and said Tehran reserved the right to respond, according to state news agency IRNA.

North Korea sanctions

Why now?

North Korea has dramatically ratcheted up its ballistic missiles testing in recent months, and last week it tested its longest-range missile yet – one that experts say could reach the US mainland.

The pariah state has warned that it could deliver a nuclear warhead on one of these missiles, prompting the US to respond with tests of its missile intercept system, THAAD, and bomber runs over the Korean Peninsula with the South Koreans.

Some of the new measures will sanction foreign entities doing business with North Korea, which could be a way of the US putting more pressure on China to stop economic activity with the country. China is the country’s biggest trading partner.

Who’s targeted?

The sanctions relate to the country’s missile testing, human rights abuses and financial institutions. There is already a long list of sanctions against North Korea imposed by the UN Security Council, and the new law tightens and modifies some of those.

Of the new additions, the President is directed to impose sanctions on people or entities that:

maintain correspondent accounts with North Korean financial institutions, with some exceptions

purchase or acquire significant amounts of certain metals and minerals form North Korea, including gold, copper and silver, as well as textiles

sell or transfer to North Korea significant amounts of rocket, aviation or jet fuel, crude oil, petroleum or natural gas, with some exceptions for humanitarian purposes

engage in online commercial activities of the North Korean government, including online gambling.

What are the sanctions?

The law reiterates existing sanctions on North Korea, such as asset blocking, including property, and the revocation of license for certain financial transactions.

The law also calls on the Secretary of State to submit a decision to Congress on whether North Korea should be designated a state sponsor of terrorism.

What’s the fallout?

US sanctions are rarely a surprise to North Korea, and there is little left to target with future sanctions.

A North Korean Foreign Ministry spokesman said in a statement on Tuesday that the US was imposing new sanctions “with the sole and impudent intention to use it as a means to seek its own interests.”

“The US threat to impose extreme sanctions on … (North Korea) only increases the latter’s vigilance and stamina, and strengthens the resolve of its people to build a powerful socialist country by dint of self-reliance and self-development.”

Andrei Lankov, a North Korea expert from Kookmin University in Seoul, said that the new sanctions were unlikely to have a major impact on North Korea.

“If we are talking about denuclearization, let’s be frank – nothing is going to work. (The) North Korean government is determined to remain nuclear, and it will remain nuclear. Period. If it means massive economic disaster, they will not care,” Lankov told CNN.

He said it was too early to say whether the sanctions would hurt the China-North Korea relationship, but he said it would likely do “serious damage” to US-China relations.

CNN’s Alexandra Field contributed to this report.