Nothing can kill the Grimace

For years, nay, decades, unhappy McDonalds customers (is there any other kind?) have been petitioning for Grimace-shaped cookies. It seems only logical - why should they not offer cookies in the shape of their coolest, most mighty and powerful mascot?
Yet McDonalds has resisted. Why?

Tasteologists at McDonalds R&D, however, know better. The restaurant has declined to comment on why they will not provide Gimace Cookies only because the truth is too dangerous. Grimace Cookies provide their eater with the most powerful diplomatic immunity known to man. That is to say, anybody eating Grimace Cookies is imbued with absolute immunity to law enforcement of any kind, including vigilante justice.

The duration of this immunity is not long. Moreover, any criminal act committed while eating Grimace Cookies is not simply erased in the memory of the law once the act itself is done. A criminal of sufficiently high-profile would likely have police and vigilantes just waiting outside of his house for him to stop eating Grimace Cookies. It follows that, to truly get away with a crime, one would have to eat Grimace Cookies constantly until the statute of limitations passes. Also, no law can be passed outlawing the act of eating them.

The result of releasing these Grimace Cookies, McDonalds knows, would result in a society of absolute lawlessness, anarchy, and extreme malnourishment. Even with sufficient vitamins taken in between cookies (even, perhaps, intraveneously), eating sugar cookies constantly cannot lead to a very long life. Therefore, a great many people would - ahem - leave the electorate, if I may borrow a euphamism from political science. What you get is:

Huge, rapid decrease in population
+
Extended period of anarchy
=
Sweet post-apocalyptic Mad Max ness.

Ladies and gentlemen, start petitioning McDonalds like you've never petitioned before.