Freedom from income taxes is among New Hampshire's delights: The Granite State is one of just nine that don't tax ordinary income. Of course, that benefit doesn't apply to New Hampshire residents who commute to work across the Massachusetts border. Income earned inside Massachusetts by an out-of-state resident is subject to Massachusetts taxes. What about a New Hampshire resident who used to commute to Massachusetts? A no-brainer, surely. If you don't live in Massachusetts, and you no longer work in Massachusetts, then Massachusetts has no right to tax your earnings. What could be more self-evident? Until last spring, that was the law. The Massachusetts Department of Revenue itself said so: "Compensation for services rendered by a non-resident wholly outside Massachusetts, even though payment may be made from an office or place of business in Massachusetts," the department affirmed in a 1984 ruling, "is not subject to the individual income tax." And if a New Hampshire resident employed by a Massachusetts company worked in Massachusetts ony part of the time? In that case, "only that portion of his salary attributable to his work in Massachusetts will be taxed."