What agreement?

This one:

We have a sign at the fuel pump as a reminder.

A signature is not required for a contract (or agreement) to be valid
and binding. There is a principle called, I believe, "detrimental
reliance", whose application here would be that if there is a sign that
says (I don't know what the actual one says) "Buying fuel here
constitutes acceptance of the following..." and you buy fuel there, you
have accepted whatever follows.

Jose
--
The price of freedom is... well... freedom.
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