International laws don't necessarily apply here. Often, multinational companies will have different classes of stock, each with its own rights (or not) to vote on major decisions affecting the company, such as a merger or transfer of stock to another company.
Without knowing more, it's hard to say whether the deal that was struck was so patently unfair that you have a right to challenge it. If that doesn't help, depending on where the company is headquartered (and where you work), there may be employment laws that speak to your rights as an employee in the event of a sale or merger of a company.
See if you can find any documentation (like a prospectus) that outlines your rights as a shareholder and consult with an attorney who is familiar with these kinds of situations.