A group seeking autonomy for Poland's Upper Silesia will go on despite a Supreme Court barring its legal registration, the group's leaders say.

Organizers of the Association of People of Silesian Nationality, known by its Polish acronym Sons, said Friday in Opole, Poland, they would continue to push for recognition as a legal group in the face of the court ruling, broadcaster TVN 24 reported.

The Supreme Court Thursday ruled that because Silesians cannot be considered a separate nation, Sons could not be recorded in the National Court Register under is current name because it is "misleading."

The panel ruled the group can't be allowed to make the suggestion through its name that a Silesian autonomous state "already exists."

"The desire to gain a sense of autonomy and the full power of Silesian nationality ... in Silesia should be seen as an attempt to undermine the unity and integrity of the Polish state, which is contrary to the Article 3 of the Constitution," the court said in its decision.

The ruling struck a nerve with backers of autonomy for Upper Silesia, a region in southwest Poland with its own German-influenced dialect, history and cultural identity.

Sons was established two years ago, focusing on the 170,000 people who declared their affiliation to the Silesian nationality during the 2002 census, and is fighting for recognition of Silesians as a national minority.

The status of the Silesian dialect spoken there has been disputed, with some claiming it a distinct language and others arguing that it is simply a Polish dialect.

Sons President Piotr Dlugosz blasted the ruling, calling it a sign that official Poland regards the effort to gain regional autonomy as a threat to the state and views Silesian residents as second-class citizens.

He promised the group will continue to operate under its current name, and could appeal the decision to the European Court of Human Rights in Strasbourg, France.

"When did we stop being citizens of the Republic of Poland?" he asked reporters during a press conference in Opole. "The court isn't there to rule on whether there is any nation or not. The court is to adjudicate the legality of the actions of individuals and entities."

Sons currently has about 1,400 members, and Dlugosz said the ruling has had an unintended effect -- the association signed up 70 new members in the day after the decision, more than the previous three months combined.

"The judgment is simply outrageous and politically motivated," Jerzy Gorzelik, leader of the Silesian Autonomy Movement political party, said in a statement. The party won 8.5 percent of the vote and three seats in the Silesian voivodship, or local parliament, in 2010.

"It's hard to believe that what was issued today came in the 21st century," he said. "The authority of the Polish state has been completely drenched in mud. I am convinced ... it will be a huge embarrassment for the Polish state."

Upper Silesia -- including such cities as including Katowice, Bytom and Chorzow -- boasts booming coal mining, steel and car manufacturing industries, and is Poland's second-richest voivodship, trailing only Warsaw and Masovia.

Autonomy backers say the the region doesn't have enough say over the considerable tax funds it sends to the national government, and is being short-changed on services.

Outside of Upper Silesia, however, those seeking autonomy are viewed by some as traitors who would rather be German than Polish, the British newspaper The Guardian reported.