What did Donald Trump do today?

He proposed making visitors to the United States turn over their social media information.

Trump's State Department today published a request for comment in the Federal Register on a rule that would force legal visitors seeking visas to enter the United States to turn over their social media accounts. After the 60-day comment period ends, the proposed rule could take effect at any time.

The rule does not say exactly which social media sites would be tracked, but according to a New York Times investigation, it includes Facebook, Flickr, Google+, Instagram, LinkedIn, Myspace, Pinterest, Reddit, Tumblr, Twitter, Vine and YouTube. Visa applicants who failed to disclose every such account would be committing a federal crime.

Travel restrictions imposed by one country are usually matched by the target countries.

The rule would also require visitors from China to disclose their identities on the sites that form the backbone of social media in China. The Chinese government is building a "social credit system" in which its citizens' activities, online and off, are tracked to establish a "trustworthiness" score. 

Trump's election was due in part to data mined from 50,000,000 Americans' Facebook accounts by Cambridge Analytica, a foreign data analysis firm founded by Trump's one-time campaign manager and White House senior advisor Steve Bannon. 

Why should I care about this?

• Building databases of people's online habits and identities is what authoritarians do.

• Policies that discourage legal visitors to the United States are bad for the United States.