Almost directly after President Donald Trump was sworn into office, back in January, he issued Executive Order EO-1, more easily identified as “travel ban 1.0.”

There were long lines and protests at airports before the Ninth Circuit court of Appeals got involved and the White House withdrew the order.

Then in March, EO-2 came out, also known as Travel Ban 2.0. Appeals to that order still have to be heard in front of the Ninth Circuit and Fourth Circuits Courts of Appeals.

And Monday, we were given Travel Ban 3.0: this time, the U.S. Supreme Court has allowed the ban on travel to and from Chad, Libya, Yemen, Iran, Somalia, Syria, North Korea and Venezuela to go into effect while legal challenges make their way through the system.

So what’s different in this third version? And where are the arguments making their way through the courts?

Geoffrey Hoffman is the director of University of Houston immigration center law clinic.