[MrsEmmaPeel]

He can resign

Not willingly. Here's a list of Popes who were driven from office:

• Clement 1 -- (97 AD) ** (no real evidence).
• Pope St. Pontain resigned (235) while in exile
• Benedict 9 (1045) driven out
• Celestine 5 (1294) abdicated
• Gregory 12 (1415) resigned

Over a 2,000 year history that's an EXTREMELY short list.

[CasearianDaoist]

NO, he can step down. I do not know what you mean by "willingly." He can retire if he choses to. There is even a resignation in the list that you post here.