This opinion will be unpublished and
may not be cited except as provided by
Minn. Stat. § 480A.08, subd. 3 (2002).
STATE OF MINNESOTA
IN COURT OF APPEALS
In Re the Marriage of:
Lana Susan Higgins, petitioner,
Warren Nau Higgins,
Filed February 11, 2003
Dakota County District Court
File No. F3-93-14712
Warren Nau Higgins, 3840 Ballantrae Road, #10, Eagan, MN 55122 (appellant pro se)
James C. Backstrom, Dakota County Attorney, Valisa L. McKinney, Assistant County Attorney, Dakota County Attorney Office, 1 Mendota Road West, Suite 220, West St. Paul, MN 55118 (for respondent Dakota County)
Mark A. Carter, 810 First Street, Suite 100, Hopkins, MN 55343 (for respondent Lana Higgins)
Considered and decided by Peterson, Presiding Judge, Harten, Judge, and Halbrooks, Judge.
Appellant, acting pro se, challenges the district court’s denial of his motion for a judgment declaring that the statutes permitting respondent to have sole legal and physical custody of the parties’ minor child are unconstitutional. Because we conclude that appellant failed to show that statutes permitting sole legal and physical custody are unconstitutional, we affirm.
Appellant Warren Higgins and respondent Laura Higgins were married in 1977. They are the parents of two children, now ages 20 and 14, whose legal and physical custody was granted to respondent in the 1994 dissolution of the parties’ marriage.
Appellant moved the district court for a declaratory judgment that any custody arrangement except joint legal and physical custody is unconstitutional. The district court denied that motion, and appellant challenges the denial.
D E C I S I O N
The constitutionality of a statute is a question of law. Hamilton. v. Comm’r of Pub. Safety, 600 N.W.2d 720, 722 (Minn. 1999). Therefore, this court is not bound by the district court’s conclusion. In re Blilie, 494 N.W.2d 877, 881 (Minn. 1993). “Statutes are presumed constitutional, and [the court’s] power to declare a statute unconstitutional should be exercised with extreme caution and only when absolutely necessary.” In re Haggerty, 448 N.W.2d 363, 364 (Minn. 1989) (citation omitted). Appellant asked the district court “[t]o declare every statute in Minnesota unconstitutional that violates [his] constitutionally protected equal right to be an equal parent * * * .”  Appellant goes on to list ten statutes to which this applies, all in Chapter 518.
In alleging that he has a constitutional right to be an “equal parent,” however, appellant ignores the legal standard governing all child custody determinations: the best interests of the child. In custody cases,
the compelling state interest * * * is the protection of the best interests of the child. The paramount nature of a child’s best interests is a principle that has been part of Minnesota child welfare law for at least 100 years.
* * * *
The equal protection guarantees prevent the government from making distinctions among people when applying the law unless the distinction serves a legitimate governmental interest. In Minnesota, custody decisions are based on the best interests of the child. The focus in applying the best-interests standard is on the child, not the parents, and therefore the standard applies equally to all parents.
LaChapelle v. Mitten, 607 N.W.2d 151, 163-65 (Minn. App. 2000) (quotation and citations omitted), review denied (Minn. 16 May 2000). Because the statutes focus on the best interests of children, rather than the rights of parents, appellant’s argument does not show them to be unconstitutional. Even if parents were held to have a fundamental right to be “equal parents,” the state’s interest in protecting the best interests of their children would justify depriving them of that right. See id. at 163 (deprivation of fundamental rights may be upheld if justified by a compelling state interest).
 The parties’ dissolution has been the subject of protracted litigation. See, e.g., Higgins v. Higgins, Nos. CO-97-945, C8-97-739, (Minn. App. 3 Mar. 1998) (affirming revocation of appellant’s driver’s license as a sanction for failing to pay child support), review denied (Minn. 30 April 1998); Higgins v. Higgins, C6-96-616 (Minn. App. 3 Sept. 1996) (affirming district court’s order refusing to allow appellant to file frivolous and redundant motions), review denied (Minn. 29 Oct. 1996); Higgins v. Higgins, Nos. C6-96-616 and C1-96-720 (Minn. App. 24 Apr. 1996) (order opinion dismissing appellant’s appeal of unappealable order); Higgins v. Higgins, No. C1-95-2313 (Minn. App. 23 Jan. 1996) (order opinion dismissing appeal of one order as untimely and appeal of another as unappealable), review denied (Minn. Mar. 19, 1996); Higgins v. Higgins, Nos. C1-95-786, C8-95-1448 (Minn. App. 26 Dec. 1995) (denying appellant’s motion to modify child support and awarding attorney fees to respondent), review denied (Minn. 13 Mar. 1996).
 Appellant also asked the court for leave to file 15 other motions based on this declaration. The district court dismissed them with prejudice, but ruled on the first motion to enable this appeal.
 As a threshold matter, we note that this issue is not properly before the court: appellant failed to notify the attorney general of his challenge to the constitutionality of a statute as required by Minn. R. Civ. App. P. 144. Failure to notify the attorney general limits the constitutional challenge to an “as applied challenge.” Welsh v. Johnson, 508 N.W.2d 212, 217 n.1 (Minn. App. 1993).
 In the alternative, appellant asks the court to declare that the 6 July 1994 judgment denying him joint legal and physical custody was an unconstitutional interpretation or application of the statutes. The time to appeal from that judgment has long passed.