(dissenting). This cause concerns a governmental exaction that is difficult to label. The circuit court and the Court of Appeals characterized the exaction as a 'Tícense fee”1 and as an *166"insurance premium” respectively,2 holding in appellees’ favor under both labels. Today, the majority advises appellees that they may not recover because the "uninsured motorist fee is more in the nature of a tax than either a license fee or an insurance premium”.3 Persuaded that appellees did not have an insurance contract with the state and that the $45 exaction could not have been levied validly as either a regulatory fee or as a tax, we agree with the Attorney General’s statement4 that the exaction is best viewed as an assessment.
*167Although somewhat dissimilar from traditional "special assessments”, the exaction was levied against a specific group to meet a specific problem related to that group;5 the exaction was not, and could not validly have been, levied against this specific group for general revenue purposes.6 The money collected for the Motor Vehicle Accident Claims Fund (Fund), including the interest that should have been paid to the Fund on moneys borrowed by the state from the Fund, must accordingly be segregated from the general fund and used exclusively for the purpose for which it was intended. Once the purpose of the Fund has been *168met, any surplus remaining in the Fund, or that would have remained had the interest due the Fund been paid, should, absent legislation providing for an enlargement of the benefits consistent with the purpose of the Fund, be refunded to those assessed to create the Fund.
I
We agree with the majority’s conclusion that there is no legal or factual basis for holding that the Motor Vehicle Accident Claims Act provides liability insurance for the appellees or that the required fee established any contractual rights.7 Although the MV ACA provided benefits to the victims of uninsured motorists akin to those provided by insurance, it was not an insurance program from the standpoint of the uninsured motorist. Uninsured motorists remained primarily liable for their torts without regard to whether the $45 annual fee had been paid and were legally responsible to reimburse the Fund fully for claims that the Fund paid on their behalf. The Secretary of State had no duty to defend uninsured motorists. Unlike insurance contracts,8 the MV ACA did not provide for one party protecting another party from loss arising from named risks in return for the payment of consideration.
II
We also agree with the majority that although the authority of the state under the police power to require automobile registration is unquestioned, the exaction at issue could not have been levied *169validly as a regulatory fee.9 In Vernor v Secretary of State, 179 Mich 157, 164, 170; 146 NW 338 (1914), this Court held that a motor vehicle registration fee in excess of the cost of registering and identifying motor vehicles must be regarded as a tax. Vernor states that the Legislature may not use the police power as a "guise or subterfuge” to enact revenue-raising measures. Subsequent decisions of this Court have followed Vernor, reaffirming that regulatory fees cannot exceed the cost of the special services required by the regulation. See, e.g., Checker Cab Co v Romulus Twp, 371 Mich 232; 123 NW2d 772 (1963) (township ordinance licensing and regulating the use of taxicabs held invalid as an exercise of the police power because the revenues raised far exceeded the cost of administration and enforcement); Merrelli v St Clair Shores, 355 Mich 575; 96 NW2d 144 (1959) *170(fees for building permits found to be revenue-raising measure because they exceeded the costs of building inspection). As the title of MCL 257.1101 et seq.; MSA 9.2801 et seq., makes clear, the money collected for the Motor Vehicle Accident Claims Fund was not intended to be used for regulatory purposes.10
There is no meaningful difference between insured and uninsured motorists in terms of the costs to the state of regulating their driving. Accordingly, a regulatory scheme charging owners of uninsured vehicles a $45 fee and owners of insured vehicles a. $1 fee for the privilege of driving11 would not have been valid.
Ill
We do not agree, however, with the majority’s characterization of this exaction as a tax. Characterizing this exaction as a tax places the MV AC A in conflict with two provisions of the Michigan Constitution. This exaction from owners of uninsured vehicles, which could not have been levied validly as a regulatory fee, also could not have been levied validly as a tax._
*171Before its amendment in 1978, article 9, § 9 of the 1963 Michigan Constitution provided that
"[a]ll specific taxes, except general sales and use taxes and regulatory fees, imposed directly or indirectly on fuels sold or used to propel motor vehicles upon highways and on registered motor vehicles shall, after the payment of necessary collection expenses, be used exclusively for highway purposes as deñned by law.” (Emphasis supplied.)
The Legislature did not "define” as a "highway purpose” the payment of benefits to the victims of accidents caused by uninsured motorists. Even if it had, it is questionable that the persons who proposed and voted for this constitutional limitation intended the phrase "highway purposes” to have a meaning so collateral to the construction and maintenance of highways and bridges.12 A tax on *172the registration of uninsured vehicles to provide funds for the victims of uninsured motorists cannot be sustained consistent with art 9, § 9 of the Michigan Constitution.
The majority intimates in a footnote that this exaction might conflict with Const 1963, art 9, § 9 if viewed as a tax, but argues that the issue need not be addressed because appellees have not sought the proper relief for a validly imposed but unconstitutionally spent tax.13 That argument presupposes, however, that the exaction in question0 would have been validly imposed had the funds been used for traditional highway purposes; that is not the case. Article 9, § 3 of the Michigan Constitution provides that a tax other than an ad valorem tax must be "uniform upon the class or classes on which it operates”. A registration tax for traditional highway purposes charging some owners a $45 fee and others a $1 fee would violate that constitutional provision. For the foregoing reasons, the MV ACA exaction could not have been levied constitutionally as a tax.14
*173IV
Special assessments of specific groups to provide revenue for the benefit of specific persons or property are not considered to be "taxes” for the purposes of state constitutional limitations. Dukesherer Farms, Inc v Dep’t of Agriculture (After Remand), 405 Mich 1; 273 NW2d 877 (1979); Wikman v City of Novi, 413 Mich 617, 634, fn 9, 683, fn 59; 322 NW2d 103 (1982); Newman v City of Indianola, 232 NW2d 568 (Iowa, 1975); Heavens v King County Rural Library Dist, 66 Wash 2d 558; 404 P2d 453 (1965); Hellerstein & Hellerstein, State and Local Taxation (4th ed), pp 43-44. In Dukesherer Farms, this Court held that the Agricultural Commodities Marketing Act, MCL 290.651 et seq.; MSA 12.94(21) et seq., imposed an "assessment” rather than a "tax” because the funds came from producers directly affected by the marketing program and were required to be disbursed solely for necessary expenses incurred by the marketing program. Concluding that the special assessment was not an unconstitutional use of the taxing power, this Court, quoting a decision of the United States Supreme Court, said:
"It is inaccurate and misleading to speak of the exaction from processors prescribed by the challenged act as a tax, or to say that as a tax it is subject to no infirmity. A tax, in the general understanding of the term, and as used in the Constitution, signiñes an exaction for the support of the Government. The word has never been thought to connote the expropriation of money from one group for the beneñt of another. We *174may concede that the latter sort of imposition is constitutional when imposed to effectuate regulation of a matter in which both groups are interested and in respect of which there is a power of legislative regulation.” (Emphasis supplied.) Dukesherer Farms, pp 19-20, quoting United States v Butler, 297 US 1, 61; 56 S Ct 312; 80 L Ed 477 (1936).
Like Dukesherer Farms, this case involves an assessment to raise money to cover a particular need that has a sufficient nexus with the persons assessed to justify the imposition. If collected as an assessment, this exaction was valid.
V
It is a maxim of statutory construction that an act of a legislature should not be construed to be invalid if another construction is available. NLRB v Catholic Bishop of Chicago, 440 US 490, 500; 99 S Ct 1313; 59 L Ed 2d 533 (1979); Kent v Dulles, 357 US 116, 129-130; 78 S Ct 1113; 2 L Ed 2d 204 (1958); Posner, Statutory Interpretation — in the Classroom and in the Courtroom, 50 U Chi L Rev 800, 814-816 (1983) (suggesting that construing statutes to avoid unconstitutionality is the only canon of statutory interpretation that has merit). Because the exaction from owners of uninsured vehicles could have been validly collected as an assessment, but not as either a regulatory fee or as a tax, we would hold that the exaction was a variety of special assessment.
VI
Unlike general revenue-raising measures, special assessments create special funds designed to be used for a specific purpose. As this Court noted in Dukesherer Farms, supra, p 20 "the spending of *175sums acquired through assessment must be rigidly defined and the money collected must be segregated from all other accounts”. See also City of Searcy v Headlee, 222 Ark 719; 262 SW2d 288 (1953); Bourland v Southard, 185 Ark 627; 48 SW2d 555 (1932); Ochs v Town of Hot Sulphur Springs, 158 Colo 456; 407 P2d 677 (1965); People ex rel Drobnick v City of Waukegan, 1 Ill 2d 456; 116 NE2d 365 (1953); Campbell v Village of Green Tree, 59 NM 255; 282 P2d 1101 (1955); Chicago R I & P R Co v Stephens County Excise Bd, 165 Okla 188; 25 P2d 70 (1933); Brookings v Associated Developers, Inc, 280 NW2d 97 (SD, 1979); McGraw v Hansbarger, — WVa —, —; 301 SE2d 848, 857-858 (1983); 81A CJS, States, § 228, p 798; 42 Am Jur, Public Funds, § 79; 14 McQuillin, Municipal Corporations (3d ed), § 38.336, p 731. Accordingly, the state had a duty to segregate the Fund for the victims of uninsured motorists and to ensure that the money in the Fund was not transferred to the state’s general fund. The state disregarded that duty in 1971 when the Legislature transferred accumulated assets of the Fund to the state’s general fund.15
In addition to having a duty to segregate the Fund from the general fund, the state had a duty to ensure that the Fund earned interest on the moneys collected for the Fund.16 It is well established that money collected by virtue of a special assessment constitutes a trust fund and that the governmental body collecting the assessment is the trustee of the fund. See, e.g., Fidelity Trust Co v *176Village of Stickney, 129 F2d 506 (CA 7, 1942); Willard v City and County of Honolulu, 323 F Supp 666 (DC Hawaii, 1971); State ex rel Taylor v Robison, 59 Idaho 485, 491; 83 P2d 983 (1938); Sampson v Village of Stickney, 24 Ill 2d 134; 180 NE2d 457 (1962); People ex rel Drobnick, supra; People ex rel Anderson v Village of Bradley, 367 Ill 301; 11 NE2d 415 (1937); Lesser v Village of Mundelein, 36 Ill App 3d 433; 344 NE2d 29 (1975); Village of Dolton v Harms, 327 Ill App 107; 63 NE2d 785 (1945); Lynn v City of Longview, 15 Wash 2d 528; 131 P2d 164 (1942). It is also "well established that conduct of the Government as a trustee is measured by the same standards applicable to private trustees”. Manchester Band of Pomo Indians, Inc v United States, 363 F Supp 1238, 1245 (ND Cal, 1973). A trustee who borrows from a trust fund must pay interest. Langford v Shamburger, 392 F2d 939 (CA 5, 1968). The failure of the state to pay interest to the Fund on the money transferred from the Fund to the state’s general fund was a violation of the state’s fiduciary duty.17 To allow the staté to borrow money from a trust fund raised by a special assessment of a discrete group of persons without the payment of interest would enable it to do indirectly what it cannot do directly — to enlarge the general fund at the expense of the trust. It would subject the members of the discrete group to further assessment necessitated by a shortfall of funds resulting from the state’s use of money belonging to the trust fund without the payment of interest. It appears that if the Fund had received the interest to which it was entitled, it might currently have a surplus after providing for liabilities._
*177VII
In situations involving land improvements, when the purpose of a special assessment has been met and money remains in the special fund, the excess belongs to the persons who have contributed to the fund in proportion to the amount of their original contribution. Chicago R I & P R Co v Stephens County Excise Bd, 165 Okla 188; 25 P2d 70 (1933); Miller v City of Seattle, 50 Wash 252, 254-255; 97 P 55 (1908).18 McQuillin, supra, § 38.336, p 731, writes:
"Landowners paying special assessments to a fund to pay bonds issued to cover the actual cost and expense of the improvement in excess of the sum required, due to miscalculation or mistake, are, in equity, justly entitled to have such excess refunded to them, each landowner to receive the excess paid by him, that is, the excess should be prorated among the property owners, as it may appear that each has paid. Such money, when collected from the several property owners becomes a trust fund, to be used only for the purpose specified, and when the bonds and interest and other legal expenses chargeable against such fund have been satisfied, the balance belongs to the landowners. Each lot or parcel of land in the improvement district must bear its equal share in the total cost and no more.”
Admittedly, the Motor Vehicle Accident Claims Fund is somewhat different than a fund set aside *178for a specific land improvement because the purpose of the Fund is less well defined and those being assessed are not the direct beneficiaries. The Legislature may, as it did,19 enlarge the benefits or the time limits respecting the Fund as long as it devotes the money to purposes consistent with those for which the money was exacted. Although the question is not before us, it may even be that the persons to be benefited by the creation of the Fund could claim the right to have a court apply the Fund to the purposes sought to be served by its establishment. Absent such a claim by such persons, or such a determination by the Legislature, the money that would be in the Fund but for the state’s failure to pay interest must be returned to the class or classes of persons from whom it was excessively exacted.
VIII
Because at this time it is unclear how much surplus will remain in the Fund after its purpose has been met and the money owed to it as interest has been paid, we would remand for proceedings consistent with this opinion. If after calculating the interest owed and making provision for the benefits remaining to be paid, the circuit court finds that the Fund has a surplus, such surplus should be refunded to those from whom it was collected.
IX
In conclusion, this cause concerns a governmen*179tal exaction that cannot be readily pigeonholed as a regulatory fee, a specific tax, or an assessment. Because it could not have been levied validly either as a regulatory fee or as a tax, and because it was an assessment of a specific group to meet a specific problem related to that group, we conclude that this exaction from owners of uninsured and insured vehicles was an assessment. As an assessment, it was validly levied, but the money exacted cannot be placed in the general fund. Absent claims by the beneficiaries of this trust fund, the moneys in the Fund, including the interest that is due the Fund, less an amount equal to the liabilities of the Fund, should be refunded to those from whom it was collected.
Although no member of the appellee class would receive a large sum as a result of appellees’ success in this action, recognition of appellees’ rights today would prevent the state from unconstitutionally appropriating to the general fund money excessively exacted from a discrete group of persons. The power to assess, like the power to tax, "involves the power to destroy”.20 When the Attorney General defends the action of the state, it is a function of the private bar and civil litigation to hold that power in check.
We would remand for further proceedings consistent with this opinion.
Kavanagh, J., concurred with Levin, J._The circuit court first found that the fee represented a one-year *166license and that appellees were entitled to a 50% refund because their license was canceled halfway through the year. The Court of Appeals affirmed in part, reversed in part, and remanded. Stating that the exaction "could be said to represent an annual insurance premium” and noting that Michigan law provides that an insurer must refund the excess portion of the premium paid by the insured if a private insurance policy is canceled, the Court of Appeals agreed with the circuit court that appellees were entitled to a refund of $22.50 plus interest if the Fund contained enough money to provide both a refund of $22.50 plus interest to each plaintiff and payment of all legitimate claims filed by persons entitled to recover from the Fund. The Court of Appeals went on, however, to hold that appellees must wait for their refund until the MVACA’s three-year statute of limitations had run and those persons harmed by uninsured vehicles had recovered. Bray v Dep’t of State, 69 Mich App 172, 178-179; 244 NW2d 619 (1976).
On the second trip up the judicial ladder, both the circuit court and the Court of Appeals found that appellees had suffered a taking of property without due process because the state had "effectively terminated” a valid "contract of insurance”. Bray v Dep’t of State, 97 Mich App 33, 42; 294 NW2d 236 (1980).
Ante, p 154.
On November 10, 1981, in oral argument before this Court, the Assistant Attorney General described the exaction as follows:
"What we have is something completely different and I don’t know why it was never picked up. It was mentioned in one of our briefs in the Court of Appeals briefly, in fact just a line. But what it was is very clear. It was an assessment. Not a tax, but an assessment. And keep in mind what this Court said in Dukesherer v Dep’t of Agriculture, 405 Mich 1. The distinction between a tax and an assessment is that a tax is for general revenue purposes [and] can be used for anything. An assessment is for a very limited purpose, and it is primarily to the beneñt of those who pay the assessment. That is exactly what we have here.’’ (Emphasis added.)
As the majority notes (ante, p 159, fn 3) special assessments traditionally involve an especial benefit to the assessed group. The strength of the law, however, is its ability to adapt established doctrines to new fact situations. See generally Levi, An Introduction to Legal Reasoning, pp 1-27, 102-104. Indeed, in Dukesherer Farms, Inc v Dep’t of Agriculture (After Remand), 405 Mich 1; 273 NW2d 877 (1979) (discussed in Part IV), this Court, analogized a levy against cherry producers to provide money to promote marketing to cases concerning special assessments for street improvements, drains, and sewers, and on that basis rejected a challenge to the levy as an unconstitutional delegation of the taxing power to private persons. As set forth in Parts II and III of this opinion, the uninsured vehicle fee could not constitutionally have been levied as a regulatory fee or as a tax. Although the uninsured vehicle fee was not a traditional "special assessment” (levied for the benefit of those especially assessed) it does not follow that the incidents of such an especial exaction or assessment cannot or should not be those that attach to other valid governmental exactions, such as special assessments, that cannot constitutionally be levied as a regulatory fee or as a tax. Clearly an exaction that cannot constitutionally be levied as a regulatory fee or as a tax should not be called a tax because it is not a traditional "special assessment”.
One can agree with the majority that "[ejarmarking the proceeds of a tax for a special fund or special purpose * * * rather than the general fund does not make the exaction any less a tax”, (ante, p 161, fn 4), without agreeing with its conclusions. As set forth in Part III of this opinion, the uninsured vehicle fee could not constitutionally have been levied as a tax. Even if the fee exacted would have been constitutional as a tax, money earmarked for a specific purpose may be required to be kept in a separate fund and may not be transferable to the general fund. See State ex rel Masterson v Ohio State Racing Comm, 97 Ohio App 108; 124 NE2d 786 (1954); McGraw v Hansbarger, — W Va —, —; 301 SE2d 848, 857-858 (1983); 81A CJS, States, § 228, pp 797-799.
Ante, p 154.
See 1 Couch, Insurance (2d ed), § 1.2, pp 28-29.
Ante, p 160.
Appellees contend that they paid a $45 license fee on April 1, 1973, for the privilege of driving uninsured for one year and, on the authority of cases requiring a pro-rata refund where a license is canceled before the licensing year ends, that because the privilege was terminated midyear they are entitled to a refund of $22.50. Elsewhere in this opinion we state why this governmental exaction cannot be sustained as a regulatory fee or tax, but is valid as an assessment. Further, even if appellees did purchase for $45 a license conferring the privilege of driving uninsured, the license and privilege was not terminated midyear when the no-fault automobile liability act went into effect. The period for which such a license and privilege was granted was shortened before it began when the no-fault automobile liability act, requiring all motorists to be insured on October 1, 1973, was enacted as 1972 PA 294 and approved by the Governor on October 31, 1972. The effect of the shortening of the period for which such a license and privilege was granted was to increase the fee required to be paid annually at the time of registration of an uninsured motor vehicle to $45 for the six-month period ending September 30, 1973. (The words "for the 1966 registration year, and for each year thereafter” were eliminated by 1971 PA 19.)
The power, purpose, and intent of the Legislature to assess owners of uninsured vehicles in such amounts as was thought necessary to provide adequate money to pay the benefits mandated by the MV ACA is clear. As set forth in Parts VII and VIII, to the extent the money collected exceeds the needs of the Fund, such excess should be refunded to those from whom it was excessively exacted.
The title, in relevant part, states:
"AN ACT providing for the establishment, maintenance and administration of a motor vehicle accident claims fund for the payment of damages for injury to or death of certain persons or property damage arising out of the ownership, maintenance or use of motor vehicles in the state in certain cases”.
The owners of uninsured vehicles were first required to contribute $25 (1965 PA 198) — raised to $35 by 1965 PA 389, and to $45 by 1971 PA 19 — to the Fund annually, and until at least 1971 (see 1971 PA 19) the owners of insured vehicles were required to contribute $1 annually. MCL 257.1103; MSA 9.2803. Because more owners of insured vehicles contributed than did owners of uninsured vehicles, it appears that contributions from owners of insured vehicles aggregated approximately one-quarter of the total amount paid into the Fund over the years the fees were collected.
In Advisory Opinion on Constitutionality of 1976 PA 295, 1976 PA 297, 401 Mich 686, 705-707; 259 NW2d 129 (1977), this Court indicated that the words "as defined by law” gave the Legislature a substantial amount of flexibility in defining the term “highway purposes”. The "as defined by law” language does not, however, confer on the Legislature unlimited power of definition.
In 1978, art 9, § 9 was amended to read:
"All specific taxes, except general sales and use taxes and regulatory fees, imposed directly or indirectly on fuels sold or used to propel motor vehicles upon highways and to propel aircraft and on registered motor vehicles and aircraft shall, after the payment of necessary collection expenses, be used exclusively for transportation purposes as set forth in this section.
“Not less than 90 percent of the specific taxes, except general sales and use taxes and regulatory fees, imposed directly or indirectly on fuels sold or used to propel motor vehicles upon highways and on registered motor vehicles shall, after the payment of necessary collection expenses, be used exclusively for the transportation purposes of planning, administering, constructing, reconstructing, financing, and maintaining state, county, city, and village roads, streets, and bridges designed primarily for the use of motor vehicles using tires, and reasonable appurtenances to those state, county, city, and village roads, streets, and bridges.
"The balance * * * shall be used exclusively for the transportation purposes of comprehensive transportation purposes as defined by law.”
*172The new language makes even more doubtful the validity of the use of a specific tax on registered motor vehicles to pay benefits to the victims of uninsured motorists.
Ante, p 164, fn 5.
The majority appears to expect omniscience from appellees by requiring them to know that a majority of this Court would characterize this exaction as a tax. Considering that this exaction would have been imposed unconstitutionally had it been a tax and that the Attorney General has several times rejected the notion that this exaction was a tax, initially expressing the opinion that this exaction could only be constitutional as a regulatory fee (letter of December 8, 1970, from the Attorney General to the Chairman of the Committee on Appropriations), and most recently expressing the view that this exaction was an assessment, see fn 4, it is understandable that appellees believed some relief other than injunction to be appropriate.
Ordinarily, the proper procedure for challenging an invalidly imposed tax or assessment is to pay the tax or assessment under protest and to commence an action for a refund. Protest is not always required, however. For example, when a tax or assessment collected is in excess of the proper amount because of a mutual mistake of fact, *173or if a tax or assessment is paid under duress, no protest is required. In the instant case, appellees could not-have known that the assessment was excessive until the purpose of the Fund was met and a surplus remained. Their suit for a refund was both timely and appropriate when filed.
1971 PA 19.
The MV ACA provided that the unappropriated moneys in the Fund be deposited to earn interest. 1971 PA 19, § 3(1); 1971 PA 63, § 3(1); MCL 257.1103; MSA 9.2803. Over $2.5 million in interest was credited to the Fund in each of fiscal years 1969 and 1970, but, after the borrowing, by the state, less than 10% of those amounts was credited in fiscal year 1971.
The Legislature originally promised to pay interest on the money that it borrowed, 1971 PA 19, § 3a, but subsequently deleted the subsection providing for interest, 1976 PA 89, § 3a. MCL 257.1103a; MSA 9.2803(1).
Refunds from excessive special assessments have been provided for in legislation. See, e.g., Wylie v City Comm of Grand Rapids, 293 Mich 571; 292 NW 668 (1940); Smith v City Comm of Grand Rapids, 281 Mich 235; 274 NW 776 (1937); Blanchard v Detroit, 253 Mich 491; 235 NW 230 (1931); Thayer v Grand Rapids, 82 Mich 298; 46 NW 228 (1890). Although the Legislature has not provided for a refund of the surplus of this assessment, that does not mean that appellees are not entitled to such relief; a court of equity may grant a refund. As this Court said in Blanchard, p 495, "in the absence of statutory provision to the contrary, [the surplus from a special assessment] may be recovered, although there is no express statutory provision therefor”.
Although the no-fault automobile liability act went into effect on October 1, 1973, by virtue of 1974 PA 223 the Fund remained liable for damages arising out of accidents involving uninsured vehicles that occurred before July 26, 1974. 1975 PA 322 extended until January 2, 1976, the benefits of the act for certain actions.
M’Culloch v Maryland, 17 US (4 Wheat) 316, 431; 4 L Ed 579 (1819).