In act 3 of Ben Jonson's play Catiline, the rebels swear as a group on a raised "silver eagle" in order to transform their attack on Rome into a sacred endeavor. The action, however, is not clearly represented in the classical sources as an oath. In this article, I will argue that Jonson changes a fairly minor detail in the record to a binding pledge in order to critique the civil, political, and spiritual strictures that are imbibed in the 1606 Oath of Allegiance. First, I will argue that the eagle is redolent of both the lectern in Protestant church architecture and the recurring metaphor of James as a protective eagle in his writing; such onstage iconography associates the Oath with Militant Protestantism and James's own semiotic currency of obedience. I will then suggest that the mounted eagle activates an onomastic play on the name of William Parker, Lord Monteagle, who famously betrayed his recusant kin to expose the Gunpowder Plot, at great benefit to himself. Lastly, I will posit that the heraldic associations of the eagle sigil link the Catilinarian bond to proparliamentarian figures such as Edward Coke and Robert Cotton, the latter a friend of Jonson.