If I understand the question, you probably cannot oppose based upon a disclamed element.
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Q: "Can you oppose to an element, which the applicant has disclaimed ... ?"
R: No. The trade dress of a product or its packaging is the cumulative whole of its elements. Any opposition to the registration of that dress must be to that cumulative whole.
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I agree, no.
If this is regards to an actual opposition proceeding or one that you intend to initiate, I strongly advise seeking some help with it. These can get rather complicated quickly and even experienced TM lawyers often have to research rules and methodology.
I suggest that you consult with a lawyer in private and discuss your objectives in more detail. You can start by calling around to several for a free phone consultation, get some insights then pick the best fit to work with.
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I take it you want to oppose the disclaimer element because you claim it is distinctively yours and not properly disclaimed. You would likely need to just write a CDL to the applicant and demand they stop using your trademark and advise them it is not subject to disclaimer and cannot be a part of their mark without likelihood of confusion as to source with your mark. Except that YOU have no business writing such a letter. If you write it, you will likely end up saying or not saying something and lose your trademark. Trademark conflicts need to be handled by trademark attorneys not novices. You are here asking because you don't know enough to do this on your own. Recognize that and get an attorney.
For Sacremento, you might contact Scott Pink http://www.avvo.com/attorneys/95814-ca-scott-pink-265102.html
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