All through history people that traveled to declared ennemy states were not only barred from serving in parliament but tried for treason. I believe that iranian or syrian lawmakers are forbidden to go to Israel without risking prison. But as usual Israel is held to different standards.
Mexico sentences five men to 697 years for killings of 11 women (AP)
from the article: Arab MKs: Bid to bar trips to enemy states is 'racist'