CNN:

Ecuador also accused Mexico’s President Andrés Manuel López Obrador of interfering in Ecuadorian politics, by making “false and injurious statements” that questioned the legitimacy of last year’s elections, according to its ICJ (International Court of
Justice) filing.

From the actual complaint, para 48:

Finally, by its Head of State making false and injurious statements calling into question
the legitimacy of the elections in Ecuador, Mexico has breached the principle of noninterference in the internal affairs of other States. This is an affront against the democratic
institutions of Ecuador and Ecuador's inalienable right to choose its political system, and is
contrary to the Charter of the United Nations, the Charter of the Organization of American
States, other related instruments, and customary international law.

I suppose a lot more states could invoke breach of "the principle of noninterference in the internal affairs of other States" in similar circumstances. Is this the first ICJ (International Court of Justice) case when something like this was invoked with respect to election interference?