43. Are there limits on the amount that third parties can spend on election campaign activities?

Cödigo Electoral de la República de Panamá
Artículo 271: 
Es prohibido:
1. Que las personas naturales o jurídicas, sea a título propio o por cuenta de
terceros, contraten o donen propaganda electoral a favor o en contra de partidos
o candidatos. (...)

Article 271: 
It is prohibited:
1. that natural or juridical persons, whether in their own capacity or on behalf of third parties, contract or donate electoral propaganda in favor or against parties or candidates. (...)."

Unofficial English translation.

There is a provision banning third parties from spending on election advertising.