In one fell swoop last week, a once-sacrosanct tenet of the 1974 omnibus pension law, the Employee Retirement Income Security Act (more commonly known by its acronym, ERISA), was overturned. For its sponsors, the measure meant saving troubled multiemployer pensions heading for insolvency. For others, a change to the 40-year law that many believe banned reductions in accrued pension benefits was yet another step to ending true pension benefits.