The laws are around consent and the ability to revoke it, which can vary by the continent/country/state/city you're in as well as some other characteristics tha

The laws are around consent and the ability to revoke it, which can vary by the continent/country/state/city you're in as well as some other characteristics that may not be known at the time that the client-side code would execute. Server-side allows businesses to defer the data transfer until it's known whether specific consent is granted or revoked. It also allows you to more easily keep a record of the data shared with other parties in the event that a user withdraws prior consent or invokes a right to be forgotten. You then have the ability to tell your partners to also delete those data points.