Arbitrary, unreasonable and/or discriminatory measures
Umbrella clause
http://www.energycharter.org/what-we-do/dispute-settlement/investment-dispute-settlement-cases/107-sun-reserve-luxco-holdings-srl-v-italy/
http://globalarbitrationreview.com/article/1078767/italy-faces-another-solar-claim (requires subscription)
https://www.transnational-dispute-management.com/downloads/27271_Case_Report_Sun_Reserve_v_Italy_Award_2020.pdf