In 2009 a Russian tax attorney named Sergei Magnitsky was beaten to death in prison, having been locked up for exposing corruption involving the Russian government and oligarchs, denied medical care, and tortured in a failed attempt to make him retract what he'd said. In 2012 Congress passed the bipartisan Magnitsky Act sponsored by Senators John McCain (R-Arizona) and Benjamin Cardin (D-Maryland) to provided financial sanctions against some of the people responsible for assaults on human rights in Russia. Two years later McCain and Cardin successfully introduced a revision of the law that isn't limited to bad actors in Russia. Following U.S. leadership, similar laws were then adopted in the United Kingdom, Canada, and the Baltic states,
In October of last year, 10 senators from both parties wrote the White House a letter that began,
The Global Magnitsky Human Rights Accountability Act requires the President, upon receipt of a request from the Chairman and Ranking Member of the Senate Committee on Foreign Relations, to determine whether a foreign person is responsible for an extrajudicial killing, torture, or other gross violation of internationally recognized human rights against an individual exercising freedom of expression, and report to the Committee within 120 days with a determination and a decision on the imposition of sanctions on that foreign person or persons.
The recent disappearance of Saudi journalist and Washington Post columnist Jamal Khashoggi suggests that he could be a victim of a gross violation of internationally recognized human rights, which includes “torture or cruel, inhuman, or degrading treatment or punishment, prolonged detention without charges and trial, causing the disappearance of persons by the abduction and clandestine detention of those persons, and other flagrant denial of the right to life, liberty, or the security of person.” Therefore, we request that you make a determination on the imposition of sanctions pursuant to the Global Magnitsky Human Rights Accountability Act with respect to any foreign person responsible for such a violation related to Mr. Khashoggi. Our expectation is that in making your determination you will consider any relevant information, including with respect to the highest ranking officials in the Government of Saudi Arabia.
The Saudi government has acknowledged that Kashoggi was murdered by its agents, and it's broadly accepted that this was almost certainly ordered by Saudi Crown Prince and de facto ruler Mohammad Bin Salman al Saud, though President Trump has gone out of his way to give the prince the benefit of every possible doubt.
The administration missed the deadline to respond to the senators' letter and has publicly indicated that it has no intention of following the law, something that has angered members of both parties. A February 11 article in Politico is headlined "GOP livid with Trump over ignored Khashoggi report" and cites critical remarks from a number of senators, both Democrats and Republicans.
(For more background, see this article and this one from October. For more specifically on the Magnitsky Act, see the Wikipedia entry and this August 30 article in Time by Magnitsky's friend and business associate Bill Browder. )
Incidentally, Vladimir Putin really dislikes the Magnitsky Acts, and in retaliation for the original one, Russia stopped allowing Americans to adopt Russian children. As you probably recall, in mid-2016 Donald Trump Jr., Jared Kushner, and Paul Manafort had a meeting in Trump Tower in New York with at least five people, including Russian lawyer Natalia Veselnitskaya, in the expectation (according to a chain of emails released by Donald Trump Jr himself) of receiving information damaging to the Clinton campaign. According to later statements by Don Jr, the main topic actually discussed at the meeting was resuming those adoptions. That pretty strongly suggests the Magnitsky Act came up, and it's plausible the Russians were after a commitment from Trump to back off enforcement of the Act.