Trump bumps up global tariffs - creating more mess and uncertainty for the world

So Trump and tariffs - what's going on? Let's start with the latest development and work backwards.  The president has announced a tariff of 15% globally.

Now you might be thinking "didn't he set it at 10% on Friday?" Yes he did. But now he's raised it to 15%.

The latest pronouncement came - on Truth Social, of course - just before lunchtime on Saturday. Here's the full post and we've highlighted the key bits: What does all this mean? It's a good question and one which governments globally are asking themselves, not for the first time.

The president is using a new statute - a new avenue effectively - to levy duties on foreign goods temporarily, because the old statute, which he'd been using since Liberation Day last April, was deemed illegal. That happened on Friday when the Supreme Court (the highest court in the land) ruled by a majority of six to three that the president's methods to impose tariffs were unconstitutional.

Six of the justices ruled the tariffs exceed the powers given to the president by Congress under a 1977 law providing him the authority to regulate commerce during national emergencies created by foreign threats. So the president and his team are looking for new ways - new statutes - to recoup some of his losses (should he have to repay the tariffs - the Supreme Court, unhelpfully, did not pass judgment on this) and to replace his tariff system.

Remember this vital point: so much of Trump's policies, his power, his ability to call the world to heel has been based on his ability to strike any country he wants with crippling tariffs. So, his immediate response to the Supreme Court decision was to use a different mechanism - Section 122 of the Trade Act of 1974 to be precise - to impose 10% global tariffs.

He had the option to impose 15%, not 10%, and on Saturday, just a day after setting it at 10, he raised it to 15. Read more from Sky News:Vitali Klitschko tells Sky News his message to Donald TrumpHouston, NASA's next moon mission has a problem That can only last 150 days.

That's why he says in his social media post that he will look for new ways of levying duties. As ever with all this, nothing is clear-cut.

There are exemptions, including on agricultural products, steel and cars, but there is confusion over this as governments seek clarity. It's a whole world of mess and uncertainty, again, for the whole world..