International student visa rule change poses risk to college debt market

California has become the first state to sue the Trump Administration over a plan to revoke the visas of international students at colleges that are offering only online instruction in the fall. The policy doesn't just threaten to upend the lives of nearly a million students, it could also be disastrous for the schools' finances. CNBC's Scott Cohn breaks down the college debt market for some clues about how bad it could be.