Chrysobull

A golden bull or chrysobull was a decree issued by Byzantine Emperors and later by monarchs in Europe during the Middle Ages and Renaissance, most notably by the Holy Roman Emperors. The term was originally coined for the golden seal (a bulla aurea), attached to the decree, but came to be applied to the entire decree. Such decrees were known as golden bulls in western Europe and chrysobullos logos, or chrysobulls, in the Byzantine Empire (χρυσός, chrysos, being Greek for gold).

For nearly eight hundred years, they were issued unilaterally, without obligations on the part of the other party or parties. However, this eventually proved disadvantageous as the Byzantines sought to restrain the efforts of foreign powers to undermine the empire. During the 12th century, the Byzantines began to insert into golden bulls sworn statements of the obligations of their negotiating partners.

Notable golden bulls included:

...
Wikipedia