The following are possible grounds for an application to be challenged: 

• Conflicting registration that was filed earlier
• Mark is opposed to moral principles or public policy
• Mark uses geographical indications
• Mark has a broad meaning, i.e., generic
• Mark is conflicting with trade names
• Mark is conflicting with notorious trade names
• Mark uses protected flags, emblems or armorial bearings
• Mark is functional, not distinct, misleading, disparaging, deceptive, or descriptive