502us2$26I 01-22-99 08:32:58 PAGES OPINPGT Cite as: 502 U. S. 367 (1992) 401 Stevens, J., dissenting the sheriff filed a motion in the District Court for an order permitting double celling in the Charles Street Jail. The motion was denied. The parties then negotiated an agreement providing for a larger new jail and for a modification of the 1979 decree. After they reached agreement, respondents presented a motion to modify, which the District Court granted on April 11, 1985. The court found that modifications were “necessary to meet the unanticipated increase in jail population and the delay in completing the jail as originally contemplated.” App. 110. The District Court then ordered that nothing in the 1979 decree should prevent petitioners “from increasing the capacity of the new facility if the following conditions are satisfied: “(a) single-cell occupancy is maintained under the design for the facility; “(b) under the standards and specifications of the Architectural Program, as modified, the relative proportion of cell space to support services will remain the same as it was in the Architectural Program . . . .” Id., at 110–111. There was no appeal from that modification order. Indeed, although the Boston City Council objected to the modification, it appears to have been the product of an agreement between respondents and petitioners. In 1990, 19 years after respondents filed suit, the new jail was completed in substantial compliance with the terms of the consent decree, as modified in 1985. III It is the terms of the 1979 consent decree, as modified and reaffirmed in 1985, that petitioners now seek to modify. The 1979 decree was negotiated against a background in which certain important propositions had already been settled. First, the litigation had established the existence of a serious