The change in the US Senate dress code to allow Senators to dress like hobos. Not that they’d be inclined to approve of business casual, either.
(From the people who brought you the notion that your Harmonious Proposal of Unquestionable Justice and Incontrovertible Benignity must be presented in the correct formal register, poetic form, and exquisite calligraphy should be tossed unceremoniously into the Brazier of Insufficiency to the Mandate comes the idea that Senators who do not display the proper respect for their august institution and its solemn task, including by failure to attend in full court dress, should be thrown unceremoniously off the Defenestrative Balcony and not readmitted to the chamber until they amend said fault.)
((While it’s more for the Post-Contact Hilarity thread, I take a brief moment to note the possibility of a brief post-contact reinvention of diplomatic uniforms by some countries. Being sufficiently underdressed at the Court of Courts places you several moves behind in the Game before you’ve even started.))