Step 1: Read the facts.
A pension scheme treats employees who retired before a cut-off date differently from those who retired after it. The excluded group says this is arbitrary. We must find the main constitutional issue.
Step 2: Recall Article 14.
Article 14 guarantees equality before law and equal protection of laws. Any classification by the State must be reasonable and not arbitrary.
Step 3: See the issue here.
The scheme makes two groups based on the retirement date. The question is whether this distinction is reasonable and valid.
Step 4: Apply the classification test.
A classification is valid only if there is an intelligible differentia separating the groups, and that differentia has a rational nexus with the aim of the scheme. If either fails, it is struck down under Article 14.
Step 5: Check the other options.
Legislative competence is about who has power to make the law, not equality. The doctrine of eclipse and the doctrine of severability deal with the validity and effect of laws, not with this discrimination challenge.
Step 6: Final answer.
So the issue mainly attracts Article 14 and the principle of classification.
\[ \boxed{\text{Article 14 and the principle of classification}} \]