US President Barack Obama created international furore recently when he delivered an important address at the White House wearing a tan suit.

While his speech – which covered the crimes of ISIS crimes and the escalating Russia/Ukraine situation ­– was ignored, his casual choice of attire immediately started trending on Twitter.

• Blanchett Vanity Fair‘s best dressed woman

It’s all part of a growing global epidemic: modern society no longer knows how to dress appropriately for an occasion.

“The dress code is disappearing,” Kirstie Clements, author and former editor-in-chief of Vogue Australia, says.

“It’s not that people are consciously ignoring the rules, they just don’t know them. And they get mixed messages when looking at celebrities.”

When Kim Kardashian and Kanye West dress for the red carpet on the street, while Rihanna arrives virtually naked to black tie events, it’s easy to see how people can get confused.

“The rules come in handy when people don’t know a great deal about fashion or style, but I think people are more educated nowadays. People are far more confident in bending the rules,” Damien Woolnough, deputy editor of Elle Australia, argues.

• ‘You can’t declare war in a suit like that!’

However, while he acknowledges that style is all about experimentation, Mr Woolnough also says it’s important to pay respect to the occasion, especially if it’s a wedding or a black tie dinner.

“They are expensive events and it’s rude not to get dressed up. It’s not cool not to care.”

If you’re confused, Ms Clements recommends taking your cues from your surroundings.

“I always think you should consider the location of where you’re going and consider the history and geography,” Ms Clements says – but avoid going completely avant garde, Mad Men style.

“Australians in particular don’t do well in the middle, we do really casual or we take it too literally and get super dressed up.”

Although some still stringently uphold the rules of days past, there are a few prominent sartorial rebels who have broken the rules and caused mass confusion.

Here are the culprits responsible for the destruction of the dress code as we know it:

Celebrity weddings

While it was once considered a serious faux pas to wear white to someone else’s wedding for fear of stealing attention from the bride, now it’s standard attire.

At Kim Kardashian’s star-studded Italian nuptials to Kanye West, her bridesmaids all wore long, white gowns. Kate Middleton’s younger sister Pippa Middleton became a global phenomenon in a slinky ivory gown at the royal wedding.

Meanwhile, television star Shenae Grimes wore black to her wedding, actress Jessica Biel wore pink and Angelina Jolie effectively let her kids scribble all over her veil.

So what’s appropriate these days?

“You can wear white to a wedding but I would be quite reluctant as it’s the bride’s day,” Mr Woolnough says.

As for men, “certainly always wear a jacket”.

Lulu Lemon

While weekends were once the domain of comfortable knit jumpers, jeans and t-shirts, visit any brunch spot on the weekend and all you’ll see now is a sea of workout gear.

Thanks to the proliferation of brands like Lulu Lemon, Nike and The Upside, wearing exercise garb outside the gym is not only acceptable, it’s a fashion statement.

The rule applies head to toe, as people flout the “no hats inside” rule in favour of leather caps and visors and wear trendy Nike or New Balance sneakers with jeans – a look once considered strictly verboten.

Fast food culture

Thanks to the rise in popularity of taco trucks and burger joints, dining out has become a significantly more casual experience.

Now, the way people dress for a meal out is “an extension of comfort” according to Ms Clements, with elastic waist pants the coveted clothing item of choice.

Hipsters

Like it or not, the inimitable hipster movement is still going strong, meaning many young men and women remain indistinguishable from homeless people.

As hipsters get more competitive with their rejection of fashion rules, Birkenstocks become a closet staple, Pharrell is encouraged to wear silly hats at award ceremonies and food hygiene standards spiral downward thanks to baristas with Ned Kelly beards. Yuck!

Gabi Grecko

When Geoffrey Edelsten’s girlfriend showed up to AFL legend Tom Hafey’s funeral wearing a revealing corset dress and sky-high heels, she cemented the loss of clothing protocol at serious events.

Appropriate funeral attire – previously limited to conservative, all-black outfits – quickly became open to colour and sex appeal…not necessarily a good thing.

Note to self: do not commit this fashion faux pas if you don’t want to offend pretty much everybody except Edelsten.

Onesies

Unflattering and vaguely infantile, onesies were popularised online and quickly made their way to the closets of Gen Y.

Essentially, the complete destruction of sartorial standards was officially complete when animal onesies became acceptable, albeit unusual, streetwear.

The world was never the same again.

Do you think the dress code is dead? Let us know in the comments section below.