WARSAW — Ex-Polish president Lech Walesa and several other former leaders appealed Wednesday to the European Union to help defend the rule of law in their country under a populist government that is overhauling the judiciary.

In a statement published in the daily Gazeta Wyborcza, the former leaders said they fear that a new law regulating the Supreme Court that takes effect on July 3 will destroy the democratic system of checks and balances in Poland.

Their open letter to the European Commission says ‘‘there will be no democratic Poland without a state of law.’’

The signatories include former presidents Aleksander Kwasniewski and Bronislaw Komorowski, as well as former prime ministers, foreign ministers, and leading Solidarity activists.

Walesa was the leader of the anti-communist Solidarity movement in the 1980s and the first democratic-era president.

European Commission Vice President Frans Timmermans, who is expected to travel to Warsaw Monday for talks with Poland’s right-wing government, said serious concerns remain about Poland’s rule of law.

He added that concessions made by the Polish government on the issue are not satisfactory.

associated press