Executive Authority to Limit Entry Into U.S. Upheld in Supreme Court Decision

On June 26 SCOTUS issued its opinion in Trump v Hawaii (the "travel ban" case). The final outcome of the case -- not surprising -- is that the President has, and historically always has had, authority to control who may enter the country.
What does this mean for travelers, immigrants, green card holders, and family abroad? For most people, it will have no impact at all. The impact will be felt only by nationals from any of the countries currently listed as restricted.
The list was 8 countries, but Chad has been take off, leaving:
North Korea
The restrictions are set for review every 6 months, and each country has specific types of waivers that may be available. Importantly, the restrictions _do_not_ apply to current Lawful Permanent Residents (green card holders).