Compliance is critical, especially for children's products. For the US market, products must meet CPSIA (Consumer Product Safety Improvement Act) standards, including lead and phthalate limits. For the EU, EN71 Parts 1, 2, and 3 (Mechanical/Physical properties, Flammability, and Migration of certain elements) are mandatory. Ensure the supplier provides a Children’s Product Certificate (CPC) or a CE Declaration of Conformity. Always check for flame retardant certifications as costumes are often classified under high-risk textile categories.