U.S. President Donald Trump apparently caught a rerun of "Saturday Night Live" this weekend, and decided to tweet Sunday morning that the NBC program should be investigated by the Federal Communication Commission for parodying him so much. That's legally absurd.

But Trump's lament reflects the persistent power of the old idea that television networks should be fair to all political sides and give equal time to all candidates for office. It's worth asking: What's the current state of the law on broadcaster fairness? And beyond the law, should fairness be an objective of any kind in the era of cable news and social media?

It's important to distinguish the two legal principles derived from the federal regulation of broadcasting: the fairness doctrine and the equal-time rule.