The first sale doctrine was already reflected in both areas of law. What this decision is about is whether patents are still exhausted if you sell the product with an EULA-style list of restrictions. Lexmark argued that because they specified that the cartridges were only to be used once, they retained their rights and ability to sue. The court determined that the restrictive sale contract did not prevent patent exhaustion.
Not quite. The court determined that sale exhausts their ability to sue under patent law. They explicitly left open the possibility that they could sue (and prevail) under contract law. (The problem with suing under contract law is that they would have to sue the original purchaser, which presents significant logistical challenges.)
