Security Laws and Regulations based on Location

Say County A has stricter laws than County B, but a firm practices in both counties, is the firm held to the strictest of both laws in both counties? For example, if County B prohibits law XYZ, but County A does not. Can a firm still proceed in County A even if it would break the law if the certain action was being done in County B? Sorry if I phrased this in a confusing way.