If a Jew cooks on Shabbos, the Shulchan Aruch OC (318:1) says
המבשל בשבת [או שעשה א' משאר מלאכות] [טור] במזיד אסור לו לעולם ולאחרים מותר למ"ש מיד - One who cooks food on Shabbos [or performs any one of the other forbidden acts on Shabbos], if done intentionally, the food is forbidden to eat forever, but other people are permitted to eat the food immediately after Shabbos.
What is the halachic status of this utensil now? Does it need to be kashered? (What if it was someone else's utensil: do we say the person cannot forbid another person's utensil in this way?)
Of course if this becomes practical CYLOR