Fed. R. Civ. P. 24(a)(2) refers to impairment "as a practical matter." Thus, the court is not limited to consequences of a strictly legal nature. The court may consider any significant legal effect in the applicant's interest and it is not restricted to a rigid res judicata test. Hence, the stare decisis effect might be sufficient to satisfy the requirement. Where the case is of first impression, the stare decisis effect would be important.
A uranium mills filed petitions to intervene in an underlying action which sought injunctions to prohibit agencies from issuing licenses for the operation of uranium mills in New Mexico without first preparing environmental impact statements. The district court denied the motions on the ground that the interests of the uranium mills would be adequately represented by another intervenor. The uranium mills argued that any consequence of the underlying action would be felt by them as the largest holders of uranium properties in New Mexico. Even though a decision would not be res judicata, still it would have a stare decisis effect.
Should the uranium mill be allowed to intervene in an action where other mills were allowed to intervene due to impairment and the fact that stare decisis would bind all of the mills?
The court allowed the intervention because the uranium mills did have an interest in the case. Intervention was permitted when the applicant claimed an interest relating to transaction which was the subject of the action and he was so situated that the disposition of the action could impair his ability to protect that interest, unless his interest was adequately represented by existing parties. The uranium mills satisfied the impairment criterion. While the interest of the uranium mills and the other intervenors may have appeared similar, there was no way to say that there was no possibility that they would not be different. The possibility of divergence of interest need not be great in order to satisfy the burden imposed by Rule 24(a)(2).