LAST WEEK'S sojourn by D.C. prisoners to a privately owned institution in Pennsylvania came as a surprise to many area residents who had not heard of the new trend toward farming out corrections responsibilities to the private sector. It certainly caused a shock in Harrisburg, where Pennsylvania officials wondered what that state's obligations and liabilities were in cases where neither the prison nor the group of offenders was under their control. The legislature promptly passed a law temporarily banning new private prisons and restricting the two existing facilities to holding only Pennsylvania prisoners convicted of certain enumerated offenses.

A moratorium on new private facilities is exactly what the American Bar Association House of Delegates recommended at its mid-year meeting in Baltimore last month. The lawyers want governments to wait "until the complex constitutional, statutory and contractual issues are developed and resolved," and they are right. There are now more than 30 such institutions in the country, but the concept has growing support among legislators, budget cutters and -- this is a significant factor -- investors, some of whom are convinced that there's a lot of money to be made in providing this service.

Why the rush to place inmates in the control of private corporations? Some say the government can save money because the private sector can build facilities faster, for less money and can operate them at lower cost without the inefficiency that government bureaucracy often causes. It is usually easier, too, to finance a correctional program out of appropriations, as could be done by contracting out the service, than by issuing bonds, which require voter approval. Finally, some believe that governments can avoid liability in lawsuits brought by prisoners by having someone else take over the task.

The objections to private prisons, however, are far more numerous and very serious. It is unlikely, for example, that courts will absolve governments from liability if private organizations are really providing a government service, as they would be doing here. Some other rather obvious problems with private prisons were raised by the ABA: What standards will govern the operation of the institutions, and who is responsible for enforcing those standards? Will the public retain both access to and ultimate power over what goes on in the prisons? How will security be maintained, and who will enforce discipline -- including loss of good time? What will happen if a private facility on which a government has come to rely raises prices, goes bankrupt or has a strike? Ultimately, and most important, is it constitutional -- or even right -- for a government that takes away a man's liberty to walk away from the responsibility of directly caring for him while he is in custody? All these questions must be debated and decided before more private prisons are opened.