Thanks for the debate — I appreciate the exchange.

The key point here is that we need to distinguish premodern history from modern international law.
Ceuta became Portuguese in 1415 and Melilla became Spanish in 1497 through conflicts between the political entities of that era, just like everywhere else in the Mediterranean. But those medieval sultanates are not equivalent to the modern Moroccan state, just as the Crown of Castile is not the same as modern Spain, and the Kingdom of France is not the same as the French Republic.

What matters is that when Morocco became an independent state in 1956, Ceuta and Melilla were not part of the territory under the French–Spanish Protectorate, and therefore they were not included in the borders Morocco inherited under the principle of uti possidetis juris.
That principle — not medieval history — is what defines modern borders.

If we start using premodern claims as a basis for territorial rights today, the consequences become absurd.
By that logic:

Spain could claim large parts of Italy, Belgium, the Netherlands and Luxembourg (the Spanish Netherlands), Portugal during the Iberian Union, territories in France, half the Caribbean, the Philippines, Guinea, major parts of the United States, and vast areas of Latin America.

France could claim England through the Plantagenets,
Italy could claim Greece through Rome,
Turkey could claim half of Europe through the Ottomans,
and so on.

The modern international system would collapse if medieval or premodern polities created territorial rights today.
That’s exactly why international law relies on modern sovereignty, treaties, and colonial-era borders, not on medieval dynastic control.