§ 10003.Pending and subsequent proceedings.

CPLR 10003 has three parts. It applies the CPLR to all actions commenced after its effective date. It also applies the CPLR to further proceedings in actions that were already pending, except to the extent a court determines that applying the new procedure to a particular pending action would not be feasible or would work injustice, in which case the former procedure, the just-repealed Civil Practice Act and Rules of Civil Practice, applies instead. And it protects proceedings already taken in an action before the CPLR's effective date: those steps are not rendered ineffectual or impaired by the change in law.

This is what lawyers mean by a 'saving clause.' When a legislature repeals or replaces a body of procedural law, a saving clause keeps that change from unwinding what already happened under the old law. Without one, a litigant who had filed a pleading or taken a deposition under the Civil Practice Act before September 1, 1963 might have had to wonder whether the CPLR's arrival wiped out that step. CPLR 10003 answers that question directly: it did not.

The section also builds in judicial discretion for the awkward middle case, a lawsuit filed before the CPLR but still moving through the courts when it took effect. Rather than force every pending case onto the new procedure regardless of the consequences, CPLR 10003 lets a court keep the former procedure in play where switching would not be feasible or would work an injustice on the parties.

CPLR 10003 operated across a single transition, the one fixed by CPLR 10005's September 1, 1963 effective date, and it has no pending cases left to apply to today. Its value now is mostly historical, though the underlying approach it reflects, applying new procedural rules to pending cases going forward while guarding against unfairness in the transition, echoes any time New York substantially revises its procedural rules.