"Supersede" (with one e!) is not the right word, I think, because that would mean to replace the provisions of the law in question. That is not what is involved here; the question is whether the notorious Cargo UE261, introduced by Ryanair, can take priority over the relevant provisions of the law (LCGC, the Ley sobre condiciones generales de la contratación). The right word, in my opinion, is "override".

Whether "artículos" of a law should be called articles or sections is a matter of opinion, which has been debated here before. Strictly speaking, the equivalent of an "artículo" in a Spanish law is a "section" in a British law; however, many people feel that this can cause confusion, and that it is better to use the calque "articles", since "secciones" has a different meaning in Spanish laws. On the whole I now share that view, though either could be used.

You can't really say "is invalid to override" (or "for overriding"). I think the best way to handle "inhábil" is probably "cannot legitimately override".

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Note added at 1 hr (2012-11-06 13:42:49 GMT)
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"Treaties cannot legitimately override the Bill of Rights."
https://www.planetdebate.com/evidence/category/13286

"The court also distinguished minors from adult students, holding that because colleges and universities have no duty to supervise the activities of their adult students, the duty of supervision required of school districts which would ordinarily override section 831.7 was inapplicable."
http://faculty.fullerton.edu/lorozco/lawglaeser.pdf

The issue here, to put it slightly tendentiously, is that Ryanair sought to use Cargo UE261 to evade the provisions of arts. 5 and 7 or the LCGC, and the court is denying the validity of this.