If this is Clean Access Agent (are people still running that?), it may (should) be possible to add your MAC address to an exemption list, and your network administrator may be willing to do that.

Though, if they haven't already offered it, then it's likely they're not going to, or they're using a newer product that doesn't have that functionality.

(I used to have to put people into exemption lists because Perfigo/CCA would want a particular Windows Update to be installed, even though it had been superceded by a newer update. Newer and better NACs just check that Windows Update is on, but it sounds like this isn't a NAC situation as much as an announcement/MOTD type of portal letting you know you're on $INSTITUTION's wifi and to agree to these rules. CCA can do that, but that was typically its secondary function, and the bulk of its work was checking for a/v defs and Windows updates.)