Updated June 27, 2017 15:58:26

Photo: US President Donald Trump says the new ban is a "victory for national security." (Supplied: White House)

The US Supreme Court has reinstated part of President Donald Trump's travel ban.

So what does it actually mean for travellers to the US?

Here's a quick look.

What does this travel ban do?

The justices of the court said the travel ban will go into effect "with respect to foreign nationals who lack any bona fide relationship with a person or entity in the United States".

"All other foreign nationals are subject to the provisions of [the executive order]."

So, it's good news if you have a provable connection to the US.

That's expected to include people with prior family, school or work connections.

But it still means that people from Libya, Iran, Somalia, Sudan, Syria and Yemen and refugees with no ties to the country would be barred from entry.

And it's also likely to set off a new round of court disputes over anti-terror efforts and religious discrimination.

However, Professor of Law at the University of Michigan Law School Margo Schlanger told RN Breakfast it would impact a very small group of people.

"What the Supreme Court did was say 'We're going to narrow the pause that's been put on that travel ban. We're going to narrow it so people who have no connection to the US, they can still be banned'," Professor Schlanger said.

"Hardly any of those people can come here anyway.

"I think this was a victory for the plaintiffs in this case.

"I just think very few of our visitors have no connection to the United States."

When will it kick in?

Last week Mr Trump said the ban would take effect 72 hours after being cleared by courts, so it should come into effect on Thursday morning local time.

What about refugees?

Part of the 120-day ban on refugees is also being allowed to take effect on a similar, limited basis.

"The Supreme Court ruling said the same rule will apply to refugees," Professor Schlanger said.

"Most refugees, I think, have a connection to the United States … so I think what this will mean is not very much.

"What will happen is in the first instance the Department of Homeland Security and the Department of State will make the judgements and then it will be up to the Federal trial court on refugees … and I would expect to see quite a bit of litigation over the next couple of months … figuring out which refugees are on which side of the line.

"Practically, this is a victory for the civil rights groups because most of the people who were going to be able to come here are going to be able to come here anyway.

"But I will say that symbolically the idea that a certain part of this Muslim ban order is going to stay in effect for at least a while is not a very attractive idea from a civil rights perspective."

What's the difference with this ban and the last two?

It's a watered-down version of both.

The first ban ordered by President Trump on January 27 put a blanket ban on people from Iraq, Libya, Iran, Somalia, Sudan and Yemen and indefinitely halted the acceptance of refugees from Syria.

It was blocked by a judge in New York just a day later, and by February 3 US District Court Judge James Robert blocked the ban nationwide.

The second travel ban was put in place on March 6, but stopped the exclusion of people from Iraq.

On March 15 it was blocked.

Is Trump happy a version of his ban has been allowed?

Yep.

In a statement, Mr Trump called the high court's action "a clear victory for our national security," saying the justices allowed the travel suspension to become largely effective.

"As President, I cannot allow people into our country who want to do us harm," Mr Trump said.

"I want people who can love the United States and all of its citizens, and who will be hardworking and productive."

Is this ban the final one?

Nope.

The President is still hoping to enforce the full ban at some point.

And in October, the justices of the court will hear full arguments on why it should go ahead.

But Professor Schlanger said the move was more about politics than national security.

"The Trump administration keeps saying what's at stake in this case is National Security, but the President did not ask the Supreme Court for a speedy resolution of the case, she said.

"The President asked the court to hear the case in October … if the President really thinks if what's at stake is national security then why wouldn't he ask for it to be heard in June or July?

"So the result is most of the travel ban remains not implemented and that will continue through to at least October …

"I don't think they're worried about the national security between now and October because there actually isn't much national security benefit from this travel ban.

"Really, it's a piece of political rhetoric to look like you're doing something without actually accomplishing much except insulting our Muslim neighbours."

ABC/wires

Topics: donald-trump, world-politics, government-and-politics, federal-government, united-states

First posted June 27, 2017 11:00:11