It questioned the validity of Spain's entire legal system, which, they claim, threatens to water down reforms which recognise Catalonia as a nation and enforce the use of the Catalan language. The editorial comes ahead of a constitutional court ruling that is expected to reject those changes, which were approved in a 2006 referendum in Catalonia.
Political reform was later ratified by the Catalan and Spanish parliaments as well as the national Senate.
A law suit opposing the reforms was later lodged with the court by Spain's main conservative opposition, the Partido Popular.
The editorial, addressed to the whole of Spanish society, claims any court ruling against political reform would put at risk the peaceful co-existence of the regions and nations of Spain.
It questions the role of the constitutional court, which, it says, threatens the legitimacy of parliaments and the civic will expressed in polls.
But a conservative association of judges lambasted the editorial as "an intolerable pressure" aimed at intimidating magistrates.
The newspapers that carried the editorial, including the nominally conservative Barcelona daily La Vanguardia, were backed by Catalan radio and TV stations, political parties, unions and civic associations.
But the Madrid daily newspaper El Mundo has accused the Catalan press of publishing false information.
"It would be impossible to say more fallacies with the worst intention in less space," said El Mundo, a paper that is close to the Partido Popular.
Spain's socialist prime minister Jos Luis Rodriquez Zapatero, however, said he has "a lot of respect" for the views expressed in the editorial.
Analysts fear a court ruling against political reform which would provide Catalonia with powers over its economy, language and taxes, could generate further support for a recently renewed independence campaign.