Grupo Modelo threw a kink in Anheuser-Busch and InBev’s weekend takeover talks by agitating over what it says is its right, under Mexican law, to give its consent to the deal.

Modelo’s claim may be tenuous, based on the terms of the contract it signed when it first agreed to adopt Anheuser as a financial partner. But because InBev is determined to keep Modelo happy, the Mexican brewer’s efforts are likely to pay off.