The right to appeal is a statutory right. [definitional]
The right to appeal is a statutory right, not a constitutional right. The Supreme Court has repeatedly recognized that a defendant may waive constitutional rights as part of a plea bargaining agreement. It follows that a defendant may also waive statutory rights, including the right to appeal.
Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide …, loc. 1120