The country can impose fines or block products from being sold in their domain if a company goes against these kinds of rulings. Same with other countries and the EU, that’s why companies ask for permission.

After Brexit they must lost a lot of leverage however. Makes me wonder when the first company will consider the potential loss of UK sales as less than the benefit of whatever deal they’re making.

the sheer size of the deal means it’s subject to a lot of regulatory scrutiny, as summarized on wikipedia. microsoft plans to appeal this but given that neither the EU nor FTC seem interested in letting it happen either, we seem to be headed toward a scenario where litigation kills the deal entirely