In order to qualify for the child tax credit, the child must be a qualifying child and you must be able to take a dependent exemption for the child. For this purpose, "qualifying child" has the same meaning as for the dependent exemption, and thus Internal Revenue Code (I.R.C.) section 152 applies here.
In the case of the adopted child under your set of facts, he or she is is not a qualifying child because the requirement that the child must have the same principal abode as you for more than 6 months of the year has not been met. This rule applies whether the child is a citizen, resident, or non-resident alien (as determined by the tax rules, not immigration rules).
The regulation you cited, Treas. Reg. § 1.152-2(c), does not change this result. The reason is that this regulation was issued in 1960, when I.R.C. § 152 was significantly different than it is now. In particular, the 2004 changes (which were effective in 2005), created two different categories for the dependent exemption, a "qualifying child" and a "qualifying relative" test. Prior to those changes, the test for the dependent exemption was a single standard which looked very much like the "qualifying relative" test. Under that old test, how long a child lived with you during the year did not matter (except in the case of divorced or separate parents); all that mattered was whether you provided over half the total support for the child for the year. That's why, in the case of an adopted child who was a citizen or resident of the U.S., under the old rule it did not matter how long the child resided with the taxpayer. So long as the person was the taxpayer's child and the taxpayer provided over half the total support, the taxpayer could take the dependent exemption. The example in Treas. Reg. § 1.152-2(c)(3) merely applies the rule that an adopted child is treated as a blood child of the taxpayer in the year of the adoption, so that if (prior to 2005) the taxpayer provided over half the total support, the taxpayer would get the dependent exemption, regardless of how long the child lived with the taxpayer, if the child was a U.S. citizen or resident. But the 2004 act changed the rules, and that old regulation cannot override the clear language of the statute.
The regulation example still holds true today when applying the "qualifying relative" test for the dependent exemption. In order to do that, the child could not be the "qualifying child" of any taxpayer. The example just does not apply for a "qualifying child." The problem is, of course, that while you might still get the dependent exemption for the child using the qualifying relative test, you could not get the child tax credit because the child must be your "qualifying child", not your "qualifying relative." Congress made a choice to limit the tax credit to taxpayers with "qualifying children," and in doing so changed the qualification for the credit from what existed before 2005. That affected more than just taxpayers with adopted kids, by the way.
Since the child was not born in the U.S., he or she is not a citizen of the U.S. It is not clear where the child was living prior to September from your facts. If the child resided in the U.S. for less than 183 days during the year, he or she was not a resident of the U.S. for tax purposes, either. If the child was neither a citizen nor resident of the U.S. for 2009, then rule of I.R.C. § 152(b)(3)(B) comes into play and requires that the child have shared the same abode with you as a member of your household for the entire tax year. The example of Treas. Reg. § 1.152-2(c)(3) does not help you because the child in that example was a U.S. resident and as a result, the requirement imposed by I.R.C. § 152(b)(3)(B) did not apply. The example specifically notes that to be the case. However, had the child been a newborn, the rule of Treas. Reg. § 1.152-2(a)(2)(ii) would have helped you, as it states that:
The period during the taxable year preceding the birth of a child shall not prevent such child from qualifying as a dependent under this subparagraph. Moreover, a legally adopted child who actually becomes a member of the taxpayer's household during the taxable year shall not be prevented from being considered a member of such household for the entire taxable year, if the child is required to remain in a hospital for a period following its birth and if such child would otherwise have been a member of the taxpayer's household during such period.
If the child was born prior to the start of the tax year, however, that rule doesn't help you.
LoneOne:Really just annoyed as to why it was obvious
to claim an adopted child as a "qualified
child" before 2005, but after 2005 they
didn't make specific exemption from the
residency requirement in the code section
similar to the one for a new born.
For a foreign adoption, the same rule in I.R.C. § 152(b)(3)(B) applied prior to the 2004 changes and the result would have been the same. There was no exemption from the residency requirement prior to 2005.