Scholars have differed over the legal status of the iqāma.
Ibn Rushd states in al-Bidāya:
“According to the jurists of the main centers, for both individuals and congregations it is an emphatic sunnah—more strongly stressed than the adhān. The Ẓāhirīs, however, deem it obligatory. I am unsure whether they consider it an obligation in the absolute sense or one of the integral pillars of the prayer. The practical difference is that on the first view, omitting it does not invalidate the prayer, whereas on the second it does. Ibn Kināna, a Mālikī scholar, said: ‘Whoever deliberately abandons it, his prayer is invalid.’”
He continues: “The apparent purport of the ḥadīth of Mālik ibn al-Ḥuwayrith indicates that it is obligatory—either for congregations or for a lone worshipper.”
I say: What is correct is that it is obligatory for a congregation, not for the individual, because the ḥadīth does not address the solitary worshipper.
Even within the Ẓāhirī school there is disagreement as to whether it is an independent obligation or one of the essential elements of the prayer, as al-Nawawī reports from al-Maḥāmlī. Al-Nawawī also transmits that Dāwūd ibn ʿAlī said: “It is an obligation linked to congregational prayer, but it is not a condition for the prayer’s validity.”
I add: Ibn Ḥazm explicitly holds that it is a condition for the validity of the prayer, just like the adhān. Preceding him in this view were ʿAṭāʾ and al-Awzāʿī, for they both said: “If one forgets the iqāma, he must repeat the prayer.” Yet this stance is not compelling. The sound position—as Shaykh al-Islām Ibn Taymiyya explains in al-Ikhtiyārāt—is that it is a communal obligation (farḍ kifāya), and this is the evident view of Aḥmad and others.
Ibn al-Mundhir likewise ruled: “It is obligatory for a congregation, whether in residence or on the road.”