A government agrees with a group of US investment funds to severely retard new (i.e. green field) housing construction for a period of X years as part of a deal whereby the investment funds buy surplus new housing left idle or unfinished after the 2008 property & construction crash. The government's idea is to use the funds' money to recapitalize banks in their state whose capacity to lend has been decimated by negative equity on their existing mortgages after the 2008 property crash. The government is hoping that once banks have funds to lend, the many unsold "for sale" homes will begin to be bought and the reduction in surplus housing stock will cause an increase in house prices in general. This will in turn lead to a gradual removal of negative equity in the mortgages in the state, more liquidity in banks' funds and an upturn in the economy in general as consumer confidence returns.
The government's plan initially works. "For Sale" signs come down from houses successfully sold. House prices start to rise as demand (more precisely, home buyers ease of getting a mortgage) rises to meet available supply of existing homes for sale. The wider economy benefits too with more new enterprises starting and an increase in expansions of existing enterprises. In fact, house prices start to rise sharply as the wider economy rebounds far quicker than the government expected. To make matters worse, the government agrees to accept a very generous quota of war refugees from Syria, Afghanistan and Ukraine. The state now has an acute scarcity of housing of all kinds for a ballooning population - yet it is "locked in" to its original agreement with the US investment funds to have minimal greenfield housing site development.
My question is can this government reasonably argue that its original sovereign agreement to build minimal new greenfield housing for X years was based on conditions prevailing at the time of that deal and that the dramatically differing new demand for new housing makes it legitimate to discontinue that deal so the state may satisfy the vivid need of its citizens for housing?