12.3 Prior use
The federal bar against registration of a mark resembling that of a prior user is primarily a codification of common law. An applicant cannot obtain rights in a mark that another person has not abandoned if use of that mark use of that mark by the applicant would be likely to cause confusion, mistake, or deceit. Thus, the prior use bar for federal registration involves the following factors:
(a) the possibility that the prior use has been abandoned ,
(b) likelihood ( not necessarily the actuality ) of
(c) confusion, mistake, or deceit
(d) as applied to the applicant’s goods, not in the abstract.
A mark is deemed abandoned only if acts of abandoned as well as an actual intent to abandon are present. Even if an owner has failed completely to use its mark, the abandonment exception will not apply unless the owner has no intent to use the mark anymore. In other words, nonuse does not constitute abandonment by itself. Beech-Nut Packing Co.(1927). However, two consecutive years of non-use raise a presumption of abandonment. The doctrine of excusable nonuse mitigates even that long a period of nonuse if the prior user can demonstrate that the nonuse was only a temporary withdrawal from the market that was caused by external forces. Upon a showing of two years’ abandonment, the burden to rebut the presumption is on the prior user who must demonstrate an intent to resume use.
Assuming the prior user has not abandoned the mark , an applicant cannot gain registration if the mark so closely resembles thar of the prior user that is likely to be confusing, deceitful or cause mistake. Since a likelihood of confusion is enough to bar the registration, evidence of confusion never is required, although it clearly can be highly persuasive. Likelihood of confusion traditionally is determined on the basis of seven elements. There are (1) similarity of marks, (2) similarity of products, (3) area and manner of concurrent use, (4) degree of care likely to be exercised by consumers, (5) strength of the mark. None of these factors is dispositive by itself. International Kennel Club v. Mighty star, Inc. (1988).
Whether a mark is likely to cause confusion will depend in part upon the similarity of the marks. Clearly, identical marks will be very likely to confuse. The more dissimilar the marks are, the less likely confusion is. The more similar the products are, the more likely a mark will be confusing, assuming some similarity between the marks. Not surprisingly, a sliding scale has been developed by which similarity of both product and mark are measured. When the products are identical, only an approximate similarity of mark need be demonstrated, since a consumer is likely to be confused when similar marks are found on identical goods. Similarly, a consumer is likely to be confused when identical marks are used even if the goods are not at all the same, although some connection is required between the goods in terms of consumer expectations.

12.3在先使用
联合禁止注册与在先使用人的商标之相似商标主要源自习惯法的法典化。如果注册商标申请人对该商标的使用将可能导致混淆、误认、欺骗时，在他方未放弃该商标使用期间，其不能获得该商标权。因此，联合注册对在先使用的商标之禁止包括下列因素：
(1) 在先使用已经存在放弃之可能性，
(2) 相似性（无需具备放弃之事实）
(3) 混淆、误认、欺骗
(4) 已适用于申请人的商品，而不是概括抽象的

视商标之放弃仅当以行动来放弃及当前有实际放弃之意向。虽然商标权人完全没有使用该商标，除非商标权人不再企图使用该商标，否则不视为放弃之例外。换句话说，不使用并不意味放弃。参见比纳包装公司(1927)之案例。但是，连续两个未使用将导致视为放弃。如果使用在先人能够证明不使用仅因来自市场的外在压力所致之临时撤回，可辩解不使用学说减轻商标长期之不使用之责任。基于两年放弃之公告，对该视为放弃持反对意见者即使用在先者承担必须证明其有意恢复使用之责任。

如果在先使用人并未放弃该商标，且申请人所申请注册的商标与在先使用人的商标近似且极易导致混淆、欺骗、误认的，不予以注册。因为混淆之可能性足以禁止注册。尽管，混淆可能明显令人信服，但混淆之证据从来不作要求。传统混淆之可能性的判定基于如下几个因素：
（1） 商标相似性，
（2） 产品相似性，
（3） 同时使用之地区及方式
（4） 消费者对商标使用之关注度，
（5） 商标的实力
上述没有一个因素单独可以确定混淆之定义。参照国际养狗俱乐部与强大之星有限公司之案例（1988）。

商标是否可能引起混淆在一定程度上取决于商标之间的相似度。显然，同一商标很容易混淆，商标之间的差异越大越不容易混淆。如果商标之间具有一些相似性，那么，产品之间相似越多，商标越可能产生混淆。勿用惊讶，产品和商标之相似性的测算方法已经不断累进。当产品相同时，仅需要证明商标的近似同一性；因为当同一商标适用在同样的商品上时，消费者很容易被其弄混淆。同样地，虽然按照消费者的期望，商品之间存在某些联系的话，即使相同的商标使用在不同商品上时，消费者也可能被其弄混淆。