Is it permissible to organize a stock exchange conference sponsored by companies, including usurious banks, brokerage firms, and food companies?

The ruling on whether it is permissible or not for a usurious bank to invite people to a conference depends on the intention behind the invitation and the conference, and whether it is to discuss matters that are Islamically permissible or not. If a company's sponsorship of the conference is a promotion of its prohibited activities, such as those of a usurious bank, then it is not permissible.