An informal arrangement between the Bush administration and previous Israeli governments allowed for so-called natural growth, but discouraged large-scale land acquisitions outside the boundary lines of the established settlements.
Under an agreement between the Bush administration and former Israeli Prime Minister Ariel Sharon, joint U.S.-Israeli teams tried to delineate those boundaries, which are rarely well-drawn, but the process got bogged down and eventually was abandoned.
One view is that the Obama administration is now insisting on a full settlement freeze from Israel to induce confidence-building gestures and steps toward normalization from the Palestinians and crucial neighboring Arab states.
It's far from clear that Netanyahu has the will or the political backing to deliver a full freeze.