b. Precautionary Principle

Precautionary Principle

Concept

The precautionary principle addresses environmental risks before full scientific certainty is available. Under the Rio Declaration, uncertainty does not, by itself, justify delaying preventive action when the threatened damage is serious or irreversible. The approach is directed toward protection of the environment, not toward waiting for harm to become certain before considering a response. (Principle 15, Rio Declaration)¹

Governing provisions

Principle 15 of the Rio Declaration calls for the precautionary approach to be widely applied by States according to their capabilities. It identifies the circumstance in which scientific uncertainty must not be used to postpone cost-effective measures to prevent environmental degradation: a threat of serious or irreversible damage. (Principle 15, Rio Declaration)¹

Requisites / Rules

• Purpose: The approach is applied to protect the environment. The measures contemplated by Principle 15 are preventive measures against environmental degradation. (Principle 15, Rio Declaration)¹
• Qualifying threat: The provision refers to threats of serious or irreversible damage. Its rule on scientific uncertainty should be stated with that qualification, rather than as a rule for every possible environmental concern. (Principle 15, Rio Declaration)¹
• Uncertainty: A lack of full scientific certainty is not a reason to postpone the measures described in the provision. Principle 15 does not require certainty of damage before States consider those measures. (Principle 15, Rio Declaration)¹
• Response: Principle 15 speaks of cost-effective measures to prevent environmental degradation and directs States to apply the approach according to their capabilities. Both limits form part of the stated rule. (Principle 15, Rio Declaration)¹

Distinctions

Principle 15 focuses on how to respond to a qualifying environmental threat despite incomplete scientific certainty. Principle 2 separately states that States have both a sovereign right to exploit their resources under their environmental and developmental policies and a responsibility to ensure that activities within their jurisdiction or control do not damage the environment of other States or areas beyond national jurisdiction. Keep the uncertainty rule of Principle 15 distinct from that responsibility under Principle 2. (Principle 15, Rio Declaration)¹ (Principle 2, Rio Declaration)²

Key doctrines

The operative point is narrow: where serious or irreversible damage is threatened, lack of full scientific certainty cannot serve as the reason for postponing cost-effective preventive measures. The provision also expressly accounts for differences in State capabilities when calling for wide application of the approach. (Principle 15, Rio Declaration)¹

Bar tip

In an answer, identify the qualifying threat, the scientific uncertainty, and the proposed cost-effective preventive measure; do not omit the reference to State capabilities. (Principle 15, Rio Declaration)¹