Trump announced a long list of planned executive orders and other measures that will restrict entry into the U.S. for asylum-seekers, refugees and migrants trying to cross the U.S.-Mexico border. Many of these moves − such as invoking the Alien Enemies Act, a law from the 1700s that is used during wartime to remove noncitizen enemies − were expected.

And some of the changes took immediate effect. Migrants who had already arrived at the U.S. border and had scheduled appointments to begin their asylum application process found yesterday that their appointments were canceled.

But many of Trump’s proposed changes run contrary to U.S. federal law and will likely be met with many legal challenges, according to Jean Lantz Reisz, an immigration scholar at the University of Southern California.

“People have the right to seek asylum under U.S. law, and by shutting the border down, the president is preventing people from exercising that right,” she told me. In our interview, Reisz explains Trump’s new executive orders, as well as the legal obstacles he may face in implementing them.

Trump promises to end birthright citizenship and shut down the border – a legal scholar explains the challenges these actions could face

Jean Lantz Reisz, University of Southern California

While the president has a broad range of immigration and national security powers, he cannot change US law on his own.

• Lessons from ‘stop and frisk’ can help Philly police use drones to improve safety without compromising civil liberties

  Robert Kane, Drexel University; Jordan Hyatt, Drexel University

  The Philadelphia Police Department plans to expand its use of drones, including as first responders.

• Learning your political opponents don’t actually hate you can reduce toxic polarization and antidemocratic attitudes

  Michael Pasek, University of Illinois Chicago

  A new video intervention shows correcting Americans’ exaggerated views of political opponents can defuse tensions, reduce support for antidemocratic practices and promote a healthier democracy.

• Electrolyte beverages can help your body stay balanced − but may worsen symptoms if you’re sick

  Bryn Beeder, Miami University

  Electrolyte beverages can be a big help for athletes and during flu season – but some may worsen issues such as diarrhea.

• Why is obesity linked to irregular heart rhythms? Researchers found 1 potential mechanism

  Arvind Sridhar, University of Illinois Chicago

  Obesity can put strain on the heart, resulting in an increased risk of conditions such as atrial fibrillation, or irregular heart rhythms.

Agriculture secretary oversees food production, rural life, and nutrition programs that help millions afford healthy diets

Kathleen Merrigan, Arizona State University

The USDA oversees food production and much more. However, it has little direct power to reduce food prices – a centerpiece of President Trump’s cam

• Wildfires ignite infection risks, by weakening the body’s immune defences and spreading bugs in smoke

  Christine Carson, The University of Western Australia; Leda Kobziar, University of Idaho

  Wildfires can unleash hidden health threats, including promoting the spread of infections.

• I’m an economist. Here’s why I’m worried the California insurance crisis could trigger broader financial instability

  Gary W. Yohe, Wesleyan University

  Central bankers agree that climate change poses a threat to the financial system. An insurance crisis is exactly the kind of problem that could spread.

• How nonprofits pitch in before, during and after disasters strike

  Vanessa Crossgrove Fry, Boise State University

  Large organizations often partner with local nonprofits that are uniquely positioned to mobilize quickly, leveraging their deep understanding of community needs and established trust with residents.