The speaker/writer has in a mind a situation in which a judge is presented with a precedent. In the context of that situation, it is the precedent, the one to which the judge must attend.
However, "the judges" is not the idiomatic way to refer to "judges in general".
A better way to state things is:
Judicial restraint is the idea that judges must pay close attention to
Plural "judges" without article means "judges in general" and singular "precedent" without article means "the concept or notion of precedent", or "previous decisions that fall under the rubric 'precedent' ".