MADRID—Spain's constitutional court struck down a regional parliamentary resolution declaring Catalonia a "sovereign political and legal" entity, auguring further battles over the wealthy region's plan to hold a referendum on independence.

Catalan leaders responded defiantly to the decision Tuesday by Spain's highest judicial body to void a resolution passed by the Catalan parliament in early 2013, saying they would move ahead with plans to hold a nonbinding independence vote on Nov. 9.

...