It happens. A lawyer sends a C&D letter, or serves a UDRP that relies on a "Registered Trademark". It shows up in the USPTO database, but it may not really be a trademark. How is that possible? When the "trademark" is registered on the "Supplemental Register".
The United States Trademark Act provides for the registration of trademarks on either the "Principal" or "Supplemental Register". Unlike Principal Register registrations, Supplemental Register registrations do not enjoy any prima facie or conclusive presumptions of validity or exclusive right to use the mark.
When the USPTO examiner indicates that the applied-for mark is clearly descriptive and as such does not qualify to be registered on the Principal Register, an applicant may choose to have its mark recorded on the Supplemental Register.
As held in First American Real Estate Solutions L.P. v. Manila Industries, Inc., NAF Claim Number: FA0607000758614¸ “Under United States trademark law, “[r]egistration of a mark on the Supplemental Register does nothing to enlarge the substantive rights of the registrant. Clairol, Inc. v. Gillette Co., 389 F.2d 264 (2d Cir. 1968). To the contrary, registration on the Supplemental register shows that at the time of registration the mark was descriptive and had not acquired secondary meaning. CyberTrader, Inc. v. Bushell, D2001-1019 (WIPO Oct. 30, 2001)”. Registration of a mark on the Supplemental Register is an admission that the mark is “merely descriptive” (See for example; America’s Community v. Charles R. Wing , WIPO Case No. D2000-1780; and Quester Group, Inc. v. DI S.A.,WIPO Case No. D2010-1950).
As held in, Tarheel Take-Out, LLC v. Versimedia, Inc., WIPO Case No. D2012-1668, “it is well settled that a Supplemental Registration in the U.S. is not sufficient in itself to establish that a Complainant has rights to a mark for the purposes of the Policy”. Registration of a mark on the Supplemental Register is not evidence that a complainant owns rights that come within the meaning of “rights” in Para. 4(a)(i) of the Policy (See; Jahnke & Sons Construction, Inc. v. Trachte Building Systems, Inc., NAF Claim Number: FA0910001292233).
Accordingly, just because a party has a "registered" trademark does not mean that it is an actual distinctive mark if it is only on the Supplemental Register, absent any proven common law trademark rights. Moreover, if a Complainant has no registered trademark rights whatsoever as far as the UDRP is concerned, it cannot rely upon its Supplementary trademark registration in order to try to meet the first part of the three-part UDRP test.
Always check to see if the trademark that is being relied upon is on the Principal or Supplemental Register.
 See also, Advance News Service Inc. v. Vertical Axis, Inc., WIPO Case No. D2008-1475 (holding that a Supplemental Registration for RELIGION NEWS SERVICE did not provide sufficient rights under the Policy to confer standing); PC Mall, Inc. v. Pygmy Computer Systems, Inc., WIPO Case No. D2004-0437 (holding that a Supplemental Registration for MOBILE MALL did not provide sufficient rights under the Policy to confer standing); Rodale, Inc. v. Cambridge, WIPO Case No. DBIZ2002-00153 (holding that a Supplemental Registration for SCUBADIVING.COM did not provide sufficient rights under the Policy to confer standing); see also WIPO Overview of WIPO Panel Views on Selected UDRP Questions, Second Edition (“WIPO Overview 2.0”) section 1.1.