The move by President Andrzej Duda raised the stakes in a standoff between Poland and the European Commission, which has asked the EU’s highest court to freeze the new rules.
Critics have claimed that the disciplinary measures could undermine judicial independence and allow the government to gag dissenters.
But Poland's governing, conservative Law and Justice party, which came to power in late 2015 and won a second term last October, has insisted that sweeping changes are needed to reform an inefficient and sometimes corrupt judicial system tainted by the communist past.
Under the new law, judges could face penalties for criticising government changes to the judiciary and challenging the appointment of those of their peers who took up their posts after the conservatives came to power.
Prime Minister Mateusz Morawiecki has warned that if judges question the appointment or verdicts of other judges, the Polish justice system could be engulfed by chaos.
The new rules are part of broad changes to the country’s justice system that have triggered a series of clashes between Warsaw and Brussels.
Opposition parties had appealed to the Polish president not to sign the measures into law.
Poland’s prime minister said last year that some of the legal changes made by his conservative government have met with criticism abroad because they are not understood in Western Europe.