What was the key issue that prompted the eu to take the helms-burton dispute to the wto?

The Helms-Burton Act punishes other countries for interaction with Cuba following the downing of two planes carrying members of anti-Castro organizations in the US. The Act opens up members of other countries to lawsuits and other problems for interaction with Cuba. The EU brought this issue to the WTO because they feel the US is exercising excessive control over interactions between other countries by controlling access with Cuba.