The Michigan Court of Appeals decided Clarke v Clarke, 297 Mich App 172 (2012) on June 26, 2012. In this decision, despite the fact that the tax exemption had been agreed to be alternated between the parties in odd and even numbered years, the court of appeals makes clear that the tax exemption is related to the child support and can be modified by the trial court.
IRS Publication 501 (a downloadable PDF file) makes clear that to be entitled to the tax exemption according to the federal tax code, a parent must have custody of the child for more than one half of the year, and it was this requirement that was the rationale for the Clarke panel’s decision. For the rules regarding the exemption, see IRS Publ. 501 at Table 5. "Overview of the Rules for Claiming an Exemption for a Dependent." [Page 12]