The phrase "lawful activity" means engaging in actions or doing things that are allowed and approved by the law. It refers to any behavior or activity that is legal and not prohibited or against the rules set by the government. Full definition
Oklahoma Dept. of Agriculture and enforcement: If you look at Title 21, you will find: «The provisions of this section shall not apply to lawful activities of any governmental agency or employees or agents thereof carrying out their respective duties under the law.» (tulsapetsmagazine.com)
«Because money is fungible, once funds obtained from illegal activity are combined with funds from lawful activity in a single account, the «dirty» and «clean» funds can not be distinguished from each other,» the decision states. (timesunion.com)
10) demanding any form of conduct or observance which makes it difficult or impossible for adherents (particularly children) to take part in lawful activities which are commonly enjoyed in British society, and punishing or attempting to punish adherents for failing to comply with such a demand, particularly by putting them in fear of supernatural disfavour. (politics.co.uk)