“ But this burden would exist only if a foreign corporation sought exemption in New Jersey on the basis of its nonprofit status at home. It is one thing for a State to avoid this extra burden by refusing to grant such an automatic exemption. It is quite another to deny a foreign corporation an opportunity equivalent to that of a domestic corporation to demonstrate that it meets the requirements for a nonprofit corporation under local law. ”

“ This Court has consistently held that while a State may impose conditions on the entry of foreign corporations to do business in the State, once it has permitted them to enter, 'the adopted corporations are entitled to equal protection with the state's own corporate progency, at least to the extent that their property is entitled to an equally favorable ad valorem tax basis.' Wheeling Steel Corp. ”

“ Yet New Jersey has denied the appellant a tax exemption which it accords other nonprofit corporations solely because of the appellant's foreign incorporation. This is not a case in which the exemption was withheld by reason of the foreign corporation's failure or inability to benefit the State in the same measure as do domestic nonprofit corporations. ”