Conflict of Interest - How to deal with it

Juan, when I first read the post I thought that the partner offering the gift worked at the same organization as your colleague, in which case I would not have seen any immediate conflict of interest. However, if the internal partner then asked your colleague for special favors or worse, to bend the rules or misrepresent the project status, that would be a conflict and your colleague would be obliged to do the right thing for the project even if it meant returning the gift.
On the other hand, if the partner is external, i.e. at a client or potential client, then I would suggest that your colleague politely return the gift as a well-intentioned and much appreciated gesture (even if it isn't either one!), and explain that it might be misunderstood by others. The PM should also report the attempted gift to their immediate manager since this external partner may try this tactic with others at the organization. It might also be an opportunity to suggest that the organization, even if small, should develop and adopt a more formal code of ethics or process for handling external gifts -- they might even want to use the PMI Code of Ethics and Professional Conduct as a model!

Hi Juan, this is such a contemporary topic that most of the PMs can have a confusion with. I think there must have been some guidelines on accepting such souvenir or gifts which may be permissible from specific set of stakeholders involved in the project. Those guidelines must be clear to all parties and form ground rule of project.

Its also important to note the intent of the activity under the umbrella of these guidelines. Is it a mal-intent or something else?

In any case, we need to be ethically correct for the project and project team to get its credibility.

El conflicto de intreses es una realidad empresarial y personal, que debemos atender teniendo en cuenta nuestros principios éticos y las prácticas de la organización. No se puede establecer una práctica general aplicable a los conflictos de intereses. La recomendación es comentar e informar el posible conflicto a los superiores, siempre teniendo como fundamento el codigo de ética de la organización si lo tiene, y los principios éticos sujeto en cuestión. Es de anotar que si el que ofrece es miembro del PMI se debe dar cuenta de esta situación Al PMI. En principio estos ofrecimientos se deben rechazar de una manera adecuada

Juan, a great question.
I believe that the best next step would be to provide this feedback to your organisation (manager) and then respond appropriately. It would be encouraged to influence for a code of ethics to be introduced into the organisation, using the wealth of information that PMI have developed. Then introducing someone who is fully responsible for Ethics (Manager / Director / Chief position) as well as a Ethics Committee would start the process of ethical behaviour within an organisation and guide partners / vendors / clients on what is deemed ethical behaviour.