This Practice Note considers the substantive standards of investor and investment protection under the Energy Charter Treaty (ECT). It does not cover the notions of the investor and investment, the denial of benefits and the dispute resolution mechanism under the ECT, which are considered in a separate Practice Note: Investment treaty arbitration under the Energy Charter Treaty. The Practice Note considers the following protections under the provisions of the ECT: fair and equal treatment and constant protection and security, within which are considered: non-impairment of investments, non-discrimination (or non-discriminatory treatment), key personnel protection, war losses compensation, and expropriation under the ECT.