The constitutional court rejected challenges by lawyers defending activists to demand the penal code provision be abolished for allegedly suppressing freedom of speech guaranteed under the basic law.
Emir Sheikh Sabah al-Ahmad Al-Sabah is described as "immune and inviolable" in the Kuwaiti constitution.
"It is not acceptable that the highest position in the country should be treated like other individuals," the constitutional court said in a written verdict.
The court, whose rulings are final, added that failure to protect the Kuwaiti ruler could threaten the unity of the oil-rich Gulf state, its internal security and the regime itself.
In April, Human Rights Watch called on Kuwait to scrap the article and stop considering "offending the emir" as a crime.
The New York-based watchdog said criminal prosecution for peaceful criticism of public officials violates international standards for human rights.