Standard equitable trademark defenses include of unclean hands, estoppel, laches and acquiescence. To trigger these defenses certain, specific factual situation must arise.

Unclean hands is a defense to a Lanham Act infringement suit. Trademark law's unclean hands defense springs from the rationale that it is essential that the plaintiff should not in the use of his trademark, or in advertisements and business, be guilty of any false or misleading representations. To show that a plaintiff's conduct is inequitable, the defendant must show that the plaintiff used the trademark to deceive consumers. Bad intent is the essence of the defense of unclean hands.

An example of a misleading representation could be a geographically deceptively misdescriptive mark. If the underlying mark was geographically deceptively misdescriptive the alleged infringer may then advance the unclean hands defense.

A defendant may raise an estoppel defense can in many situations as estoppel is not a purely trademark infringement defense.

For example, if a trademark owner tells a potential defendant that it will not assert a claim of infringement based on the use of a particular mark, and the recipient of that assurance relies on the assurance to its substantial detriment, such as by spending substantial sums in the development of the mark, estoppel will bar the trademark owner from subsequently claiming infringement.

Thus, as mentioned above, the estoppel defense will only arise in very narrow circumstances.

Laches is essentially a statute of limitation for trademark actions because the Lanham Act (the source of US Trademark Law) does not have a statue of limitations. To determine whether or not laches is applicable, courts first determine when the statute of limitations period expired for the most closely analogous action under state law. If the plaintiff filed within that period, there is a strong presumption against laches. If the plaintiff filed outside that period, the presumption is reversed. The court then must balance the following six factors to determine whether the trademark owner's delay in filing suit was unreasonable and, therefore, barred: (1) strength and value of the trademark rights asserted; (2) plaintiff's diligence in enforcing mark; (3) harm to senior user if relief is denied; (4) good faith ignorance by junior user; (5) competition between senior and junior users; and (6) extent of harm suffered by the junior user because of senior user's delay. The party asserting laches must demonstrate that it has suffered prejudice as a result of the plaintiff's unreasonable delay in filing suit.

While most of these factors are self explanatory, two require further explanation.

     Beginning of the Laches Period

The laches period typically begins when the plaintiff knew or should have known about the harm. For example, a plaintiff is certainly put on notice when the parties have plants in the same city and plaintiff had many business contacts with defendant.

     Plaintiff's Diligence in Enforcing Its Mark and Progressive Encroachment

The second factor, plaintiff's diligence in enforcing the mark, implicates a further, more complex test. That is, whether or not plaintiff's delay is explained and excused by the doctrine of progressive encroachment.

Under this doctrine, the trademark owner need not sue in the face of de minimis infringement by the junior user. The owner may wait until the junior user of a mark moves into direct competition . . . selling the same 'product' through the same channels and causing actual market confusion. Common methods of encroachment are the junior user's expansion of its business into different regions or into different markets. However, a junior user's growth of its existing business and the concomitant increase in its use of the mark do not constitute progressive encroachment.

     Conclusion

When such a burden has been met, the defendant will successfully avoid a claim for trademark infringement, because they have, in effect, created a statute of limitations for a claim of trademark infringement.

The defense of acquiescence in a trademark infringement case requires proof of three elements: (1) the plaintiff actively represented it would not assert a right or claim; (2) the delay between the active representation and assertion of the right or claim was not excusable; and (3) the delay caused the defendant undue prejudice. The difference between acquiescence and laches is that laches denotes passive consent and acquiescence denotes active consent.

The representation that the plaintiff would not assert a claim may either be express or implied.