Informal institutions govern property rights and disputes when formal systems are weak. Well-functioning institutions should help people reach and maintain bargains, minimizing violence. Can outside organizations engineer improvements and reduce violent conflicts? Will this improve property rights and investment? We experimentally evaluate a UN and civil society mass education campaign to promote alternative dispute resolution (ADR) practices and norms in rural communities, where violent land disputes are common. Prior work showed a fall in violence and unresolved disputes within one year. We return after three years to test for sustained impacts and channels. Treated communities report large, sustained falls in violent disputes and a slight shift towards nonviolent norms. Treated residents also report larger farms, though overall effects on property rights and investments are mixed. Politically-connected residents report more secure property rights while those with fewer connections feel less secure. Sustained social engineering is feasible but politics shapes distributional outcomes.