The trustee of an inter vivos trust brought this action in the Probate and Family Court Department for Suffolk County, seeking a declaratory judgment that a child bom out of wedlock to the donor’s granddaughter is “issue” of the donor’s children for purposes of the trust. The nonmarital child remains illegitimate because her paternity has never been acknowledged and her parents have never intermarried.2
The parties named as defendants include all the living beneficiaries of the trust. None has answered, although all have been served with notice. A guardian ad litem (guardian) was appointed to represent the interests of the donor’s minor issue, and he has opposed the relief prayed for by the trustee. A guardian ad litem also was appointed to represent the nonmarital child; he has adopted the arguments advanced by the trustee. The parties signed a statement of agreed facts, and the Probate Court judge granted their joint motion pursuant to Mass. R. Civ. P. 64, 365 Mass. 831 (1974), for reservation and report of the case to the Appeals Court. We granted direct appellate review.
*652The facts agreed are these. On May 7, 1959, the donor established an inter vivos trust that, by its terms, was to be construed according to the laws of the Commonwealth. The trust instrument provided for payment of income to the donor for life, then to her surviving children in equal shares for the duration of their lives, and then to the children’s “issue” by right of representation. The indenture of trust also authorized the trustee “to pay to or for the benefit of the children of the Donor and their issue such amounts of principal as the Trustee . . . may deem necessary for comfort, maintenance, support and education without reduction of the interest of the recipient in income and principal.” The trust is. to terminate twenty-one years after the death of the donor’s last surviving child, whereupon the trustees are to convey the share of each of the donor’s children to that child’s issue by right of representation, notwithstanding prior unequal distributions of principal.
The donor died on August 5, 1969. She was survived by one son and two daughters, one of whom still survives, and nine grandchildren, all of whom survive.3 On July 14, 1973, a unmarried granddaughter of the donor gave birth to a daughter (nonmarital child). The nonmarital child has never been the subject of legitimation, paternity, or adoption proceedings. She has resided with her mother in Vermont, in close proximity to her maternal relatives, who have accepted her as a member of their family circle.
Distributions of principal to the nonmarital child are sought to provide for her support and education. Such distributions were made in the past on joint requests from the child’s mother and grandmother, the trustees then being unaware of the child’s nonmarital status.4 It is undisputed that the nonmarital child is illegitimate, both by the law of this Commonwealth and by the law of Vermont, the State of her birth and the only domicil she has known.
The trustee advances several alternative arguments in support of the declaration he seeks.5 We discuss each in turn.
*6531. The donor’s intent. “It is fundamental that a trust instrument must be construed to give effect to the intention of the donor as ascertained from the language of the whole instrument considered in the light of circumstances known to the donor at the time of its execution.” Groden v. Kelley, 382 Mass. 333, 335 (1981), relying an Dana v. Gring, 374 Mass. 109, 117 (1977), and cases cited. Our review of the trust instrument confirms what is undisputed here, that the instrument itself contains no indication of the donor’s intent to use the word “issue” so as to include or exclude nonmarital descendants. Additionally, assuming that evidence of external family circumstances would be competent, we note that the existence of the nonmarital child was not known to the donor at the time she executed the instrument, the child having been bom after the donor’s death.
In these circumstances, the trustee argues that, absent extrinsic evidence establishing that the donor ascribed a special meaning to the term “issue,” her intent “must have been to use [it] in its usual and customary meaning as generally used, meaning biological issue, regardless of legitimacy, ‘progeny’ or ‘offspring,’” citing Webster’s New Int’l Dictionary (2d ed. 1947). While we take judicial notice that the dictionary meaning of “issue” does not exclude nonmarital children, and it did not at the time the donor executed her indenture of trust, we know of no legal authority for the proposition that contemporaneous dictionary meanings must be read into the ambiguous words of trust instruments. Additionally, the statutory law of this Commonwealth is not wholly consistent with the dictionary definition of “issue” which the trustee urges upon us. General Laws c. 4, § 7, Sixteenth (1984 ed.), provides: “‘Issue’, as applied to the descent of estates, shall include all the lawful lineal descendants of the ancestor.”6 The common law mle is squarely contrary to the tmstee’s position. We have stated that “[t]he word issue . . . must be interpreted against a background *654of statutory phraseology and construction which has remained wholly consistent for well over a century.” Fiduciary Trust Co. v. Miskou, 321 Mass. 615, 635 (1947). Dealing with the question whether an illegitimate child was included within the expression, “the-issue of my deceased children,” we stated further: “We can hardly regard this as an open question in this Commonwealth. It cannot be doubted that by the common law of a few generations ago such words as issue, children, descendants, and so forth as descriptive of a class in a grant, devise, or legacy, in the absence of anything indicating a contrary intent, meant only persons of the class who were bom in lawful wedlock.” Id. at 634. This rule of construction was operative at the time the trust in question was executed, and it concludes the question of the donor’s intent. Because nothing indicates an intent by the donor to include nonmarital issue, precedent requires us to presume that the donor intended, in accordance with the law extant at the time the instrument was executed, to exclude nonmarital descendants from the class denoted by her use of the word “issue.”
2. Equal protection analysis. The trustee argues that application of the mle of construction stated in Mishou, supra, would violate the rights of the nonmarital child to equal protection of the laws as guaranteed by the Fourteenth Amendment to the Constitution of the United States.7 We disagree.
It is the trustee’s contention that the mle of construction as to a donor’s intent discriminates against nonmarital children because, taken in tandem with G. L. c. 190, § 7 (1984 ed.) (see note 2, supra), it impermissibly excludes from trust participation as “issue” all nonmarital children not expressly included unless their parents have intermarried. We do not view this argument as persuasive. The guarantees of the equal protection clause of the Fourteenth Amendment are directed solely to limiting the actions of government. See Commonwealth v. Hood, 389 Mass. 581, 584-586 (1983), and cases cited.
*655The trustee argues, nevertheless, that the rule of construction set forth in Mishou, supra, is subject to scrutiny under the Fourteenth Amendment because the United States Supreme Court has said that “State action . . . refers to exertions of [Sjtate power in all forms.” Shelley v. Kraemer, 334 U.S. 1, 20 (1948). We do not believe that the holding in Shelley is relevant here. “In Shelley, neighboring property owners sought to enforce a private, racially restrictive agreement to prevent the sale of a house by a white seller to a black purchaser. The Court held that judicial enforcement of the agreement constituted State action.” Hood, supra at 588. However, “[t]he Supreme Court has not developed Shelley beyond these facts . . . .” Id.
Shelley is inapposite on its facts. In Shelley, the Court had no doubt that State action was involved because it was clear that “but for the active intervention of the state courts, supported by the full panoply of state power, [the black] petitioners would have been free to occupy the properties in question without restraint.” Shelley, supra at 19. State action was found because judicial enforcement of the “private law” of restrictive covenants effectively barred blacks from participation in a significant segment of the housing market. In Mishou, the court reaffirmed a definition for a word whose meaning, as judicial experience repeatedly showed, would remain ambiguous without judicial clarification. Under the court’s ruling, donors and testators enjoyed freedom to use the word “issue” without explication, confident that we would enforce the instrument containing it to exclude nonmarital children. Similarly, donors have been free to modify the word by stating an additional, contrary intent, in which case we have enforced the instrument to honor that intent. When “issue” is used in a legal instrument, with or without explication, it is the donors and testators who act, not this court nor any other arm of the State.8 Thus, we hold *656that State action is not involved, nor is the equal protection clause of the Fourteenth Amendment implicated, when courts apply rules of construction to wills or trust instruments. Accord Hanson v. Markham, 371 Mass. 262, 265 (1976); Boston Safe Deposit & Trust Co. v. Fleming, 361 Mass. 172, 179 n.7 (1972).9 Therefore, no constitutional rights would be violated if the rule stated in Mishou were to be applied in this case.10
*6573. Obsolescence of the rule of construction. The trastee argues that the Mishou rale should not be applied because it is no longer appropriate to do so in light of current social mores and modem legal developments.11
The Mishou decision was handed down almost forty years ago. In the interim, this court does not appear to have reconsidered the utility or propriety of its rule that, absent clear expressions of a contrary intent, the term “issue” must be read to exclude nonmarital descendants. Indeed, the Mishou court itself did not state the principles underlying this rale of construction; rather, it merely treated the applicability of the rale as a closed question in this jurisdiction. Mishou, supra at 634. Nor was the rationale for the rale subjected to judicial scrutiny in any of the decisions relied upon in Mishou. See Mishou, supra at 634-635, citing Green v. Kelley, 228 Mass. 602, 606 (1917); Sanford v. Marsh, 180 Mass. 210, 211 (1902); Hayden v. Barrett, 172 Mass. 472, 474 (1899); Adams v. Adams, 154 Mass. 290, 292 (1891).
All these decisions treat the rale as sound because it was well settled in English and American law. We must turn to a *658decision written in 1827 for what appears to be the most recent judicial airing of the reasons for the rule:
“[Tjhere seems to be no maxim of [the common] law less questionable than that a bastard is filius nullius .... No doubt the law [barring illegitimates from inheriting as next of kin] was so established on higher principles than the interest of individuals. It was to render odious illicit commerce between the sexes, and to stamp disgrace on the fruits of it; and though the punishment usually falls upon the innocent, yet it was thought wise to prohibit them from tracing their birth to a source which is deemed criminal by law and by religion. It is enough that . . . the authors of this misfortune have the power to repair it by will or by gift; the law will not interpose.” Cooley v. Dewey, 4 Pick. 93, 94 (1827) (Parker, C.J.).
It is questionable whether the attitudes expressed by Chief Justice Parker were representative even of his own era; within two years after Cooley, the Legislature had mitigated the non-marital child’s status as filius nullius by enacting a statute which made such children heirs of their mothers for purposes of intestate succession. See St. 1828, c. 139, codified at G. L. c. 190, § 5 (legislating, as well, a result contrary to the primary holding in Cooley, supra), Monson v. Palmer, 8 Allen 551, 554-555 (1864).
Moreover, while the “source” of nonmarital birth is still deemed criminal in this Commonwealth, see G. L. c. 272, § 14 (1984 ed.) (adultery), and § 18 (1984 ed.) (fornication), “[i]t seems beyond dispute that the statutes defining or punishing [these] crimes . . . have fallen into a very comprehensive desuetude.” Fort v. Fort, 12 Mass. App. Ct. 411, 417 (1981). But see Commonwealth v. Stowell, 389 Mass. 171 (1983) (upholding constitutionality of G. L. c. 272, § 14). In this context, we question the practicality of trying to enforce morality or to preserve traditional family values by rules of con*659struction embedded in the law of trusts. Indeed, the quixotic nature of any such attempt is suggested by the facts that, while the Mishou rule has been in effect, the nationwide number of nonmarital births yearly had risen to 715,200 by 1982, and the rate of such births had more than tripled since 1960. United States Department of Commerce, Statistical Abstract of the United States 62 (106th ed. 1986).
The justice of punishing innocent children for the actions of their parents has long been questioned. Indeed, doubt was expressed in several decisions relied on by the court in Mishou. “Removal of the obstacles to the legitimation of innocent children, who have no responsibility for the circumstances of their birth, and thus ameliorating some of the apparent harshness of the common law, has been the progressive policy of our law as illustrated by statutes and decisions.” Green, supra at 605. See Gritta’s Case, 236 Mass. 204, 207 (1920) (holding nonmarital offspring not “children” within the meaning of the Workmen’s Compensation Act, but “dependents” where they were members of an employee’s family). Acceptance of the idea that justice requires nonpunitive treatment of nonmarital children is reflected in numerous Federal statutes that, over the years before and sineq Mishou, have guaranteed more nearly equal treatment.12 Similarly, although not controlling here,
*660both Federal and State decisions of more recent years give witness to a reconsideration of the harshness of the law’s treat*661ment of illegitimate children. See notes 8, 9, and 11, supra. Finally, we note that our own Legislature recently has declared in another context: “Children bom to parents who are not married to each other shall be entitled to the same rights and protections of the law as all other children. G. L. c. 209C, § 1, inserted by St. 1986, c. 310, § 16.
Thus, if the mle excluding nonmarital children from judicial construction of the word “issue” was not archaic when this court reiterated it in 1947, it has become so. We cannot say that the attitudes underlying that mle, as expressed in Cooley, supra, are so widely held in this Commonwealth today as to warrant our imputation of them to donors and testators who use the word “issue” without explication. Rather, we think that the following sentiment, voiced by the Supreme Court of the United States almost fifteen years ago, comes much nearer to the mark:
“The status of illegitimacy has expressed through the ages society’s condemnation of irresponsible liaisons beyond the bonds of marriage. But visiting this condemnation on the head of an infant is illogical and unjust. Moreover, imposing disabilities on the illegitimate child is contrary to the basic concept of our system that legal burdens should bear some relationship to individual responsibility or wrongdoing. Obviously, no child is responsible for his birth and penalizing the illegitimate child is an ineffectual — as well as an unjust — way of deterring the parent.” (Footnote omitted.) Weber v. Aetna Casualty & Sur. Co., 406 U.S. 164, 175 (1972).
Ours is an era in which logic and compassion have impelled the law toward unburdening children from the stigma and the disadvantages heretofore attendant upon the status of illegitimacy. Consequently, we think it more appropriate henceforth to place the burden of exclusion on those donors who insist on it. Therefore, we overrule so much of Mishou as depends *662upon the traditional rule of construction;13 and we conclude that the word “issue,” absent clear expressions of a contrary intent, must be construed to include all biological descendants.14
A crucial question remains concerning the applicability of the rule we announce today to the parties at bar. “[T]he general rule is in favor of retroactive application of a change in decisional law, . . . [but] [primarily because of concern for litigants and others who have relied on existing precedents, judicial changes in Massachusetts contract and property law have been given only prospective effect.” (Citations omitted.) Payton v. Abbott Labs, 386 Mass. 540, 565 (1982), and cases cited. See also Sullivan v. Burkin, 390 Mass. 864, 870-871 (1984) (statutory interpretation allowing surviving spouse to reach assets placed in inter vivos trust by deceased spouse held to apply only prospectively). The rule stated in Mishou appears to have been controlling in the Commonwealth for 150 years or more. As was said in Sullivan, supra, “The rule of Kerwin v. Donaghy [317 Mass. 559 (1945)] has been adhered to in this Commonwealth for almost forty years .... The Bar has been entitled reasonably to rely on that rule in advising clients. In the area of property law, the retroactive invalidation of an established principle is to be undertaken with great caution.” *663We conclude, then, that the new rule of construction applies only to trust instruments executed after the date of this opinion.15
The case is remanded to the Probate and Family Court for Suffolk County for entry of a declaration that, under the law applicable when the trust instrument was executed, the unexplained word “issue” is presumed to encompass only lawful lineal descendants of the donor.
So ordered.
The statute governing legitimacy in this Commonwealth is G. L. c. 190, §7 (1984 ed.), which reads in relevant part: “An illegitimate person whose parents have intermarried and whose father has acknowledged him as his child or has been adjudged his father under chapter two hundred and seventy-three shall be deemed legitimate . . . .”
The statement of agreed facts was filed on October 9, 1985. The status of the trust’s beneficiaries as “surviving” or “deceased” was current as of that date.
The grandmother of the nonmarital child died on March 26, 1985. At that time, the child’s mother succeeded (together with each of her siblings) to a one-twelfth share of the income from the trust.
The trustee raised several of these arguments in an earlier case involving other parties, but we reach these questions for the first time. See Powers v. Steele, 394 Mass. 306, 309 n.5 (1985).
The trustee argues that G. L. c. 190, § 5 (1984 ed.), must be construed to create equal status for persons bom out of wedlock where, as here, the nonmarital child claims through a female beneficiary. In pertinent part, § 5 reads as follows: “An illegitimate person is heir of his mother and of any person from whom his mother might have inherited, if living . . . .” It is undisputed that the trust at issue here involves a gift, not an inheritance. The nonmarital child is not her mother’s heir until the mother’s death. First Agricultural Nat’l Bank v. Shea, 351 Mass. 1, 3 (1966). A similar argument was rejected in Fiduciary Trust Co. v. Mishou, supra at 635-636; thus, we cannot conclude that § 5 applies to the question at bar.
In relevant part, the Fourteenth Amendment reads as follows: “No state shall . . . deny to any person within its jurisdiction the equal protection of the laws.”
But see Estate of Dulles, 494 Pa. 180, 190 (1981) (statutory rule of will construction amounts to State action in manner identical to an intestacy statute because in both instances the State steps in to supply a presumed intent, with the result that “the state and not the decedent dictates the method of distribution”). Cf. Trimble v. Gordon, 430 U.S. 762, 774 (1977).
We note that the trustee’s equal protection argument relies primarily on Trimble v. Gordon, supra, which invalidated an intestacy statute, not a judicially created rule. While we do not deny that rules applying to what has traditionally been thought of as the area of “private law” may trench upon equal protection concerns, it is instructive to note that no decision by the Supreme Court of the United States ever has. invalidated a common law rule of construction on the ground that it violated the equal protection clause by discriminating impermissibly against nonmarital children. The liberalizing decisions handed down by the Supreme Court in recent years have all been directed at statutory discriminations. See Reed v. Campbell, 476 U.S. 852 (1986) (intestacy statute); Pickett v. Brown, 462 U.S. 1 (1983) (statute of limitations on paternity suits); Mills v. Habluetzel, 456 U.S. 91 (1982) (same); United States v. Clark, 445 U.S. 23 (1980) (Civil Service Retirement Act); Lalli v. Lalli, 439 U.S. 259 (1978) (intestacy statute); Trimble v. Gordon, supra (same); Mathews v. Lucas, 427 U.S. 495 (1976) (Social Security Act); Jimenez v. Weinberger, 417 U.S. 628 (1974) (same); New Jersey Welfare Rights Org. v. Cahill, 411 U.S. 619 (1973) (State statute providing assistance to families of the working poor); Gomez v. Perez, 409 U.S. 535 (1973) (paternal support statute); Weber v. Aetna Casualty & Sur. Co., 406 U.S. 164 (1972) (Workmen’s Compensation Act); Labine v. Vincent, 401 U.S. 532 (1971) (intestacy statute); Glona v. American Guarantee & Liab. Ins. Co., 391 U.S. 73 (1968) (wrongful death statute); Levy v. Louisiana, 391 U.S. 68 (1968) (same); Beaty v. Weinberger, 478 F.2d 300 (5th Cir. 1973), aff’d, 418 U.S. 901 (1974) (Social Security Act); Griffin v. Richardson, 346 F. Supp. 1226 (D. Md.), aff’d, 409 U.S. 1069 (1972) (same); Davis v. Richardson, 342 F. Supp. 588 (D. Conn.), aff’d, 409 U.S. 1069 (1972) (same).
The trustee concedes that the Equal Rights Amendment to the Constitution of the Commonwealth does not apply to this case. See note 11, infra. Nonetheless, he claims that “[t]he common law disabilities of birth outside of wedlock require mitigation under Art. 1 of the Constitution of the Commonwealth,” due to its provision that all people “are bom free and equal and have certain natural, essential and unalienable rights; among which may be reckoned the right ... of acquiring, possessing and protecting property . . . .” It is not clear from the trustee’s brief, however, whether he asserts that art. 1 is applicable in the absence of State action. No authority is cited in support of that proposition. Compare Batchelder v. Allied Stores Int'l, Inc., 388 Mass. 83 (1983) (art. 9 of the Massachusetts Declaration of *657Rights is not by its terms directed only against governmental action), with Commonwealth v. Aves, 18 Pick. 193, 209-210 (1836) (Shaw, C.J.) (if slavery was not effectively abolished in the Commonwealth by colonial law, it was abolished by enactment of art. 1). In this state of underdevelopment, the argument is not one we would be prudent to reach. See Mass. R. A. P. 16 (a) (4), as amended, 367 Mass. 919 (1975).
The trustee argues that reversal of the Mishou rule is required by our holding in Lowell v. Kowalski, 380 Mass. 663 (1980). In that decision, G. L. c. 190, § 7, as amended through St. 1943, c. 72, § 1, was held to be unconstitutional under the Commonwealth’s Equal Rights Amendment, art. 106 of the Amendments to the Massachusetts Constitution, to the extent that § 7 required, as to heirs of the father, parental intermarriage (in addition to paternal acknowledgment or an adjudication of paternity) as a prerequisite to legitimation for purposes of intestate succession. Cf. G. L. c. 190, § 5 (right of illegitimate child to inherit from mother’s estate). The trustee concedes that the Equal Rights Amendment does not apply by its terms to nonmarital children. See art. 106 (suspect classifications are only those of “sex, race, color, creed or national origin”). Here we deal not with statutory construction, but with the interpretation of the intent of a donor. We do not see the relevance of Lowell to the question at bar, which we decide solely on the basis of our traditional authority to alter or enforce common law rules pertaining to private acts.
A representative list of such statutes was compiled in Matter of Hoffman, 53 A.D.2d 55, 62-63 n.7 (N.Y. 1976):
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In Mishou, the court stated: “If this rule of construction is deemed too harsh, the remedy is not to be found in sudden and unheralded changes by judicial decision in the meanings of words which have long been established and accepted and in reliance upon which wills have been drafted and settlements of property effected.” Mishou, supra at 636. Now, almost forty years later, we do not think the change we announce is sudden or unheralded in any way. As will become clear, infra, our limitation of the new rule to prospective application effectively obviates the Mishou court’s concern for the reliance interests of donors and testators now deceased.
In Mishou, it was observed that the traditional rule of construction was contrary to the Restatement of Property §§ 265, 286, and 292 (1940). Mishou, supra at 636. While abandoning the traditional rule, we do not adopt these sections of the Restatement. The rule we do adopt is substantially in accord with § 292, but these sections of the Restatement treat questions not reached here — for example, whether the term “children” is to be construed as including or excluding nonmarital descendants. See, e.g., §§ 286 and 292 comment a.
We note that the dissent relies primarily on authorities from other jurisdictions, and also that many of those authorities do not involve property law, where reliance on existing precedent plays a significant role in settling the rights of parties. Additionally, we have a well established body of law on the issue of retroactive application of a new rule of civil law.