Hmm...why do we even have copyright and patent laws? It's to protect the process of creativity and innovation, as no one will invest time and money if it is legal to rip off the success of others. Of course in fashion it is a lot more ambiguous, and such laws cannot be enforced as short of a blatant direct copy, nothing can be proven beyond doubt and enforced legally. It doesn't mean it cannot be called out as it hardly hurts the designers' profits, bottom line and even reputation - Proenza Schouler will go on to sell this hugely successful and popular line. However, it does mean that designers are rewarded for the wrong things, and the truly innovative designers are not rewarded for taking risks.
In fact, designers are often penalized for showing something new, different, and that goes against current trends and fashion, sorry, I am still upset about the widespread criticisms and pressure that forced out Paulo Melim Anderssen - to know why we have to go back and look at his FW2007 collection for Chloe that cost him his job, a collection that was bold, edgy, prescient and sensed the change in bigger, boxier cut, in bold paintbrush strokes and prints that lasted till this year (5 years in total), in the move away from vintage-y girlishness.
http://www.style.com/fashionshows/review/F2007RTW-CHLOE
So, good designers who take risks get booted while those who wait and watch from the side and then jump on get rewarded.
I remember NG himself was the object of severe criticism when he plagiarized Kaisik Wong's collage dress - and it was only one dress, and not a "copy and paste" job either.
I don't get why PS or MJ should be the exception?