Last month, yoga-gear guru Lululemon Athletica Inc filed a lawsuit in the US Federal Court in Delaware against PVH Corp’s Calvin Klein brand and G-III Apparel Group alleging infringement of three "design patents" (the US term for registered designs) relating to the design of its famous yoga pants. Lululemon’s design patents relate to the v-shaped waistband which features on its flagship product. An example of one of the design patents can be seen here.

The lawsuit comes after the launch of Calvin Klein’s "Performance" line of knee-length yoga pants and tights. While Lululemon’s "Astro" yoga crop pants and tights retail for $US78 and $US98 respectively, Calvin Klein’s version was retailing for $US39 and $US60 on Amazon.

If the case goes ahead, it will offer a rare insight into design patents in the fashion industry. In the US, inventors can apply for a "utility patent", which provides protection for the functionality of a product, or a "design patent", which protects the appearance of a product. Design patent protection is more expensive than copyright and trade mark protection, and requires a more detailed and time-consuming application process which would be unrealistic for most seasonal fashion designs. Nevertheless, the design patents are obviously important for the Canadian-based Lululemon, which posted a profit of $US46.6 million on sales of $US285.7 million in the first quarter of 2012.

In Australia, registered designs can provide designers with protection over the visual appearance of a manufactured garment if it is "new and distinctive". Examples of design patents granted in Australia include Crocs footwear and Review Australia wrap dresses. The application process can be lengthy and costly – but given that copying and adapting designs is commonplace in the fashion industry, implementing a design registration strategy for a distinctive feature (such as Lululemon’s) could ultimately pay off.

In a mini-victory for Lululemon, Calvin Klein has removed the specific styles mentioned in the case from its company website since the launch of the lawsuit.