To evade is to not do something- like if someone is charged with tax fraud or nonpayment, it is illegal.
Similarly, evasion of import duties, evasion of customs duty, or duty evasion is an offence someone could be charged with. This means they have not paid the duty. Evading goes beyond not wanting to pay the duty - it's not paying. From what I understand, I may be wrong, but you pay duty on imports.