The Supreme Court overturned Humphrey's Executor, allowing presidents to fire heads of independent agencies like the SEC and FTC without cause — a major shift in separation of powers. In a second ruling, the Court upheld mail-in ballot grace periods in more than half the states. Plus: Iran and the U.S. hold ceasefire talks in Doha today, the EPA eliminates its authority to regulate vehicle emissions, and the FDA approves a device that could save thousands of donor lungs currently discarded.