PORTLAND – The Maine Supreme Judicial Court on Friday struck down a property-tax relief program adopted last year by the city of Portland to benefit homeowners.

In a case heard by three of the nine justices, the court concluded that the program, which offers tax rebates of about $400 on owner-occupied homes, resulted in unequal apportionment and assessment of real estate taxes.

The court said the program also violated the state constitution by creating a tax exemption without legislative approval.

Under the program, owners of homes valued at less than $400,000 were eligible to claim a rebate on taxes owed on $15,000 of valuation. Because the rebates were financed by all Portland taxpayers, the lost revenue was made up by higher taxes on owners of commercial and industrial properties.

The case went directly to the law court on a report of agreed facts without any prior rulings by a lower court.

The three justices, Donald Alexander, Paul Rudman and Jon Levy, agreed that Portland usurped the Legislature’s authority over taxation. But Levy reasoned that the rebates were a municipal expenditure rather than an exemption and thus did not result in unequal tax apportionment.