P is a Maine nonprofit corporation that operates a summer camp for the benefit of children of the Christian Science faith. A Maine statute at issue provides a general exemption from real estate and personal property taxes for 'benevolent and charitable institutions incorporated' in the State. With respect to institutions that are 'in fact conducted or operated principally for the benefit of persons who are not residents of Maine,' however, a charity may only qualify for a more limited tax benefit, and then only if the weekly charge for services provided does not exceed $30 per person. Most P's campers come from out of State. P could not qualify for a complete exemption, and because weekly tuition was roughly $400, P was ineligible for any charitable tax exemption at all. In 1992, P made a formal request to D for a refund of taxes paid from 1989 through 1991, and a continuing exemption from future property taxes, based principally on a claim that the tax exemption statute violated the Commerce Clause of the Federal Constitution. The Superior Court ruled for P. D appealed, and the Maine Supreme Judicial Court reversed. It reasoned that the exemption statute 'treats all Maine charities alike'--given the fact that 'all have the opportunity to qualify for an exemption by choosing to dispense the majority of their charity locally'--it 'regulates evenhandedly with only incidental effects on interstate commerce.' The court considered the exemption an expenditure by the state. The Supreme Court granted certiorari.