Although Congressional officials can debate just about whatever they please, it seems that a citizen signing this would be acting in an "agency" (i.e. lobbying) capacity for foreign interests. A fine line to cross---but critical to national sovereignty. I'm not even sure that Congress men can interject into this issue outside of official debate on the Floor. There is a provision in the law for US officials acting as "agents" also. Some of them have nothing but this as an issue, and it is one that applies to foreign citizens, not US citizens.