A look at the day ahead in European and global markets from Wayne Cole.

The early Asian reaction to the utter mess that is U.S. tariff policy was to revive the "sell America" meme, with the dollar and Wall Street futures sliding.

So, the Supreme Court strikes down President Trump's signature emergency tariff policy, essentially saying he's been breaking the law for almost a year. Then Trump holds a media conference where he announces a 10% tariff on the whole world, effective from Tuesday.

Less than 24 hours later, he takes to social media to announce the tariff is going up to 15% effectively immediately, apparently wrong-footing some of his own officials. The White House on Friday posted a long list of trade items exempt from the initial 10% tariff, though it's not clear if that holds for the new 15% rate.

The bill Trump is now using, for the first time ever, specifically prevents discrimination between countries, so the whole world has to get 15%. Oddly, this now includes heavily sanctioned Russia and North Korea, which somehow missed the initial tariffs.

It also means some countries, including the UK and Australia, face higher tariffs, while many others including China could see large falls. India has put its deal with the U.S. on hold, and the European Commission ruled out changes.

This power also lasts for just 150 days before it needs to be extended by Congress, something Republican lawmakers will likely be loath to do given how unpopular tariffs are in opinion polls. White House officials have been out to say effective tariff rates will not change that much and trade deals that have already been agreed will stand. How that works given these deals were struck under tariffs that no longer exist, isn't clear.

Treasury Secretary Bessent even threatened trading partners with embargoes should they not honour these deals. Imagine, the U.S. embargoing itself from world trade. Would the U.S. navy be sent out to blockade Chinese ports? Or European ports? Might be easier for the navy to just blockade all U.S. ports.

Then there's the scramble for refunds of the circa $170 billion in now illegal tariffs paid, with more than 1,800 suits already filed with the U.S. Court of International Trade. It's also likely any money reimbursed will end up with the importing companies, not the consumers who paid the tariffs in higher prices.

The uncertainty has seen European stock futures slip 0.5%, while S&P 500 futures are off 0.8% and Nasdaq futures 1%. The market was already jittery ahead of Nvidia's earnings NVDA.O on Wednesday, which will test the resilience of the AI trade.

The world's most valuable company is expected to post a 71% rise in earnings per share in the fiscal fourth quarter on revenue of $65.9 billion. For the coming fiscal year, analysts on average expect an EPS of $7.76, though estimates range from as low as $6.28 to as high as $9.68. Options imply its shares could shift by at least 6% in either direction on the announcement.

Key developments that could influence markets on Monday:

- Appearances by European Central Bank President Christine Lagarde, Bank of England MPC's Alan Taylor, Federal Reserve Board Governor Christopher Waller

- Data includes German Ifo survey, US factory orders, Dallas and Chicago Fed surveys

(Editing by Kate Mayberry)

((Wayne.Cole@thomsonreuters.com; 612 9171 7144; Reuters Messaging: wayne.cole.thomsonreuters.com@reuters.net/))