Rabbi David Ben-Zazon has issued a ruling that it is permitted for all people to visit the entire area of the Temple Mount.
"According to the Rambam (Judaism's ultimate authority on Jewish Law), a person even in an unpurified state can enter the area of the Holy Temple, even if just to walk around. Despite the holiness of the area, there is no punishment incurred for being there," the rabbi wrote.
There is an opinion that setting foot on the Holy Temple site incurs the punishment of karet, which includes being cut off from a share in the world to come.