1. Who proposed or introduced the integration principle into EU law?
Treaty of Amsterdam
Spiegazione
The Treaty of Amsterdam (1997) formally introduced the integration principle into EU law, establishing the obligation to embed environmental protection into all EU policies. The other options, such as the Treaty of Rome, the European Parliament, and the European Commission, are plausible but do not specifically relate to the formal proposal or introduction of this principle. The Treaty of Amsterdam is the correct attribution for the formal introduction of the integration principle.