The bill now goes to the Senate.
Some Democrats, including the ranking member of the House Select Committee on Intelligence, California Congressman Adam Schiff, called for a delay in the Thursday vote because of what he called the "irresponsible and inherently contradictory messages" coming out of the White House.
"You would see the color drain out of the faces of all of our security personnel ... if we lost the ability and went dark on 702", Mr. King said.
Unmasking refers to the largely separate issue of how Americans' names kept secret in intelligence reports can be revealed.
So what's wrong with that?
Intelligence community bosses say this capability is an essential part of protecting the USA against terrorists and foreign spies.
That could happen if a citizen is communicating with a foreigner who is under surveillance, even if that foreigner isn't suspected of being a terrorist.
The reason that critics of the law are so upset is that the program essentially gives law enforcement agencies a "backdoor" to search Americans' data without having to get a warrant.
The Fourth Amendment of the Constitution protects against unreasonable searches and seizures, and officials have insisted 702 does not run afoul of it, despite skepticism from rights advocates. They must show probable cause to believe that evidence of a crime will be found. The "unmasking" refers to senior government officials asking an intelligence agency to reveal the names of Americans or US entities in a piece of intelligence to better understand the information. "This is about foreign terrorists on foreign soil", he said.
However, when "millions of Americans are incidentally collected in the database, we don't want people willy-nilly looking into this database without a warrant", said Paul. "The president doesn't feel that we should have to choose between protecting American citizens and protecting their civil liberties".
Democrats mocked Trump for his criticism of the FISA law, and his repeated claims he was subjected to it.
What did Congress do Thursday? The final vote was 256 to 164. Once it in government databases, there is a debate and an ongoing debate about what rules should apply when the government seeks to search those databases for USA persons' information, their communications in instances in which they have never obtained a warrant.
"We have a debate today about whether to put the F back in the Foreign Intelligence Surveillance Act".
The White House officially backed the former.
Lawmakers in the House are weighing whether the Federal Bureau of Investigation should have to get a warrant to either query information on Americans in the database or seek a warrant only if the Federal Bureau of Investigation wants to view the actual contents of the material and use it for investigating and prosecuting domestic crimes.
Section 702 is due to expire next week, though intelligence officials say it could continue until April.
Trump attempted to walk back his tweet about 90 minutes later, urging lawmakers in a second tweet to reauthorize the program.
The White House declined to comment on who spoke to the President on Thursday about the FISA issue.
Yesterday Trump tweeted: "This is the act that may have been used, with the help of the discredited and phony Dossier, to so badly surveil and abuse the Trump Campaign by the previous administration and others?"
On the blinking lines: Republican lawmakers and top intelligence officials perplexed that Trump had appeared to contradict more than a week of public statements from the administration in support of the reauthorization, which allows the government to conduct warrantless spying on United States soil. Although Democratic Senator Ron Wyden and Republican Senator Rand Paul have both promised to filibuster the bill in opposition, observers say it will nevertheless pass.
As Trump's morning tweet sent shockwaves through Washington, the president once again took to Twitter, this time to voice support for the 702 authority.