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Defendants typically formally respond to the plaintiff's lawsuit by filing an answer or legal documents, attempting to prove that the plaintiff's patent, trademark, or copyright is invalid, that there is no infringement, or employing a "fair use" defense.

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  • No Infringement: The most straightforward defense is to assert that the defendant's product or process does not infringe any patent claims, either literally or under the doctrine of equivalents (which posits that a product or process, although not identical in every technical detail to the original patent, can be considered infringing if it performs the same function in a substantially similar way to achieve the same result).


  • Invalidity: The defendant can argue that the patent is invalid for the following reasons:

    •          Lack of novelty: The invention was not new at the time of the patent application.

    •          Obviousness: The invention was obvious to a person skilled in the relevant field at the time of the patent application.

    •          Insufficient disclosure: The patent does not sufficiently describe the invention in detail, enabling a person skilled in the relevant field to make and use it.

    •          Ineligible subject matter: The invention does not qualify for patentable subject matter, such as abstract ideas, natural phenomena, and natural laws.


  • Prior commercial use: In some jurisdictions, if the defendant can prove that they had commercially used the invention protected by the patent before the patent applicant applied for the patent, they may be granted the right to continue using the invention, even if the patent is valid. However, if the patent was invented by researchers at a university or other higher education institution, or if the technology used or improved by the defendant was directly obtained from the patent holder, then the defense of "prior commercial use" may not apply.


  • Laches: The defendant may argue that the patent holder delayed bringing the infringement lawsuit, which caused harm to the defendant. However, after the U.S. Supreme Court's decision in SCA Hygiene Products Aktiebolag v. First Quality Baby Products, LLC, the applicability of the laches defense in patent infringement cases has been diminished.

  • Estoppel or Waiver: The defendant may argue that the patent owner made certain representations or took certain actions indicating that they would not sue the defendant for infringement, and the defendant relied on these statements or actions to their detriment.


  • Licensing: If the defendant has obtained a license to use the patent, they can defend against infringement allegations by demonstrating that they are operating within the scope of that license.


  • Exhaustion (or the First Sale Doctrine): Once a patented product is sold by the patent holder, or with the patent holder's authorization, the patent rights for that product are "exhausted," meaning the patent holder cannot control its further use or resale.


  • Permissible Repair: The owner of a patented product is allowed to repair the product to keep it in working condition without infringing on patent rights. This concept is intended to balance the rights of the patent holder with the rights of the product owner to enjoy their property. Product owners are permitted to replace worn parts and make repairs, but they cannot recreate the patented invention or make substantial modifications that amount to a reconstruction.


  • Inequitable Conduct: If the patent holder engaged in deceptive practices during the patent application process, the patent may be considered unenforceable. This defense involves proving that the patent holder intentionally concealed important information from the patent office or provided misleading information.


  • Experimental Use: In some cases, the use of a patented invention for experimental purposes, to test or improve the invention, may not be considered infringement.


  • Abuse: If the patent holder abuses their patent rights, violating antitrust laws or other unfair practices, the patent may be considered unenforceable. For example, tying the sale of a patented product to the purchase of a non-patented product.


  • Failure to Properly Mark the Patent Number: Proper marking notifies the public of the existence of a patent and is typically a prerequisite for claiming infringement damages. If a patent holder fails to mark their products, they may only be able to collect damages from the time they actually notified the infringer of the infringement, rather than from the start of the infringement. There are exceptions to this requirement, such as when marking is not feasible.



  • No Confusion: The defendant may argue that consumers are unlikely to confuse their product with the plaintiff's trademark, due to sufficient differences between the two.


  • Trademark Not Used: The defendant may point out that the plaintiff has not actually used their trademark, or has abandoned the use of the trademark.


  • Generic/Descriptive Terms: The defendant may argue that the terms they use are descriptive or generic and should not be protected under trademark law.


  • Prior Use: The defendant may claim that they used the trademark in a specific geographic area before the plaintiff, thus having priority over the trademark within that area.


  • Licensing or Authorization: The defendant may claim that they have obtained permission or authorization to use the trademark from the plaintiff.


  • Statute of Limitations: The defendant may argue that the plaintiff filed the lawsuit beyond the legally prescribed time limit.


  • Fair Use: The fair use defense in trademark infringement cases refers to specific circumstances under which the use of another's registered trademark does not constitute infringement. This primarily includes two scenarios:

    • Descriptive Fair Use: When a word or phrase is both a registered trademark of a company and a generic term used to describe a certain product or service, other companies can use this term to describe their own products or services without causing consumer confusion. For example, if "Quick Dry" is a registered trademark of a company, but another company uses "quick dry" to describe the quick-drying feature of its product, this may constitute descriptive fair use.

    • Nominative Fair Use: When using someone else's trademark to specify a particular product or service (usually for comparison, commentary, or providing information), and the following conditions are met: (a) the product or service cannot be identified without using the trademark; (b) only the necessary part of the trademark is used (no excessive use); (c) the use does not mislead the public about the origin of the goods or services. For example, a third-party product review website mentioning a specific brand's product in its reviews might constitute nominative fair use.


Regrettably, in trademark infringement lawsuits against cross-border e-commerce, U.S. plaintiffs often include these scenarios as part of the infringement, leading to collateral damage. Since foreign defendants typically opt for settlement or default judgment, they do not have the opportunity to clarify their defense based on "fair use" during the trial, resulting in the establishment of the alleged infringement by the plaintiff.

  • Plaintiff's unclean hands: The defendant may point out improper conduct by the plaintiff in obtaining or using their trademark, such as misleading advertising or deceptive practices.


  • No actual harm caused: The defendant may argue that even if infringement occurred, it did not result in any actual harm, and therefore, they should not be held liable.


  • Weakness of the trademark: The defendant may argue that the plaintiff's trademark lacks distinctiveness or strength, and therefore should be afforded lower protection.



  • Fair Use: A common defense strategy where the defendant claims their use of the protected work was solely for purposes like commentary, news reporting, education, or research, which could be considered fair use.

  • No Copying: The defendant asserts that their work was independently created, not copied from the plaintiff's work.

  • Copyright Invalid: The defendant may challenge the validity of the plaintiff's copyright, for example, by arguing the work doesn't meet originality requirements.

  • Licensing or Authorization: The defendant claims to have obtained permission or authorization from the plaintiff to use the work.

  • Statute of Limitations: The defendant argues that the infringement occurred a long time ago, beyond the legal timeframe for filing a lawsuit.

  • Lack of Copyright Rights or Ownership: The defendant claims the plaintiff did not own the work or related rights at the time of the lawsuit.

  • Exemptions or Immunity: Certain types of works may not be protected by copyright law, or some specific uses may be exempt.

  • Unforeseeable Use: The defendant argues that the use was unforeseeable at the time of the original license or authorization, and therefore should not be considered infringement.

  • Differences Between Works: The defendant highlights differences between their work and the plaintiff's to prove no infringement occurred.

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