The problem with the whole ‘Smart Casual’ thing is – as demonstrated above – pretty much nobody knows what it means (some are getting it mixed up with Business Casual), but lots of people think they do, or think they know what other people think it means. So you can be completely right and perceived by most to be wrong, even by the people who stipulated the code.
In the case of the OP – the party throwers who have made the stipulation are as unlikely as anyone else to actually know what they’ve meant by ‘Smart Casual’ and that its is a defined code, and not just an approximare way of saying ‘Don’t worry you don’t need to come in cocktail dress, just relax but try and have a wash before you arrive’
‘Smart Casual’ in its strict sense is highly conformist and specifies a very narrow spectrum of clothing – clothing that a lot of people don’t even own (who the hell, other than CHF owns a Sport Coat, dress socks or loafers?), and if you adhere to the code theres less room for interpretation than many would realise. Chinos for instance – as often mentioned above would require a very loose interpretation of the code – its Dress Trousers.
However I picked up some invaluable advice from a fashion expert on breakfast telly a few years ago. She was invited on to talk about fashion trends for the glastonbury/festival/glamping season and was reeling off blether about ‘boyfriend blazers’ and flowery wellys and the presenter asked her what fashion tips she had for men
“Men? Pffft men needn’t worry about it, if you make the effort you’ll just get it wrong.”