Because we are remanding for redetermination of the child support amount, and the wife's argument regarding the trial court's authority to award reimbursement of any overage may again arise, we address the issue. The wife's reliance upon Donovan, 152 N.H. 55, 871 A.2d 30, Walker v. Walker, 116 N.H. 717, 367 A.2d 211 (1976), and Henry v. Henry, 129 N.H. 159, 525 A.2d 267 (1987), for the proposition that a statutory change that affects substantive rights may be applied only prospectively is misplaced. To be sure, “[w]e have held previously that statutory changes affecting parties' rights to post-divorce financial support would not be applied retroactively to pre-existing divorce decrees.”

Because we are remanding for redetermination of the child support amount, and the wife's argument regarding the trial court's authority to award reimbursement of any overage may again arise, we address the issue. The wife's reliance upon Donovan, 152 N.H. 55, 871 A.2d 30, Walker v. Walker, 116 N.H. 717, 367 A.2d 211 (1976), and Henry v. Henry, 129 N.H. 159, 525 A.2d 267 (1987), for the proposition that a statutory change that affects substantive rights may be applied only prospectively is misplaced. To be sure, "[w]e have held previously that statutory changes affecting parties' rights to post-divorce financial support would not be applied retroactively to pre-existing divorce decrees."

See, e.g., Henry v. Henry, 129 N.H. 159, 161 (1987) (holding that amendments to alimony statute would apply only to orders based upon divorce decrees entered on or after the effective date of the amendments). Similarly, in Walker v. Walker, 116 N.H. 717, 718 (1976), we addressed the effect of a statutory reduction in the age of majority from twenty-one to eighteen years in determining the age of a child's emancipation. Absent any clear showing of the legislature's intent that the statute was to have retroactive effect, we held that the change in the age of majority would not affect preexisting divorce decrees under which a parent's support obligation would continue until the child became emancipated or reached the age of twenty-one.

[5-7] Where a law affects substantive rights and liabilities, it is presumed to apply only to future causes of action unless there is some evidence of legislative intent that the statute be applied retrospectively. See Harris v. Adams, 123 N.H. 167, 170, 459 A.2d 241, 243 (1983); Walker v. Walker, 116 N.H. 717, 718, 367 A.2d 211, 212 (1976). When a statutory change, however, as found in this case, solely affects procedures or remedies, rather than substantive rights, the normal presumption against retrospective application is reversed.

Byrne v. Byrne, 120 N.H. at 430, 418 A.2d at 1268. See also French v. French, 117 N.H. 696, 699, 378 A.2d 1127, 1128-29 (1977) (trial court has jurisdiction to order obligor to pay educational expenses of child who had reached adulthood); Walker v. Walker, 116 N.H. 717, 718, 367 A.2d 211, 212 (1976). The duration of an obligor's duty of support can depend not only on the terms of the decree but on the age of "majority" when the decree was issued.

Initially, we note that the divorce decree provides for the termination of child support when the children reach age twenty-one or are emancipated. Because the reference to age "would have been superfluous if coming of age had been contemplated within the meaning of emancipation," we must determine, without regard to whether the child has attained the age of majority, whether the child is emancipated. Walker v. Walker, 116 N.H. 717, 718, 367 A.2d 211, 212 (1976). [1, 2] The general rule is that a child becomes emancipated when he enters the military, at least for the period of his military service.