Pakistani constitution bars non muslims from assuming the role of Head of State and of Republic. The reason being that majority of Pakistani's are muslims (around 97%) so they should have a muslim head of state.
Although it seems logical but it would be even 'more logical' if there were no restrictions on minorities to assume this role constitutionally. Its their right being the citizen of this country. Would a minority head of state be a risk to Islam? give me a break...
What would you have.. a very good administrator (minority representative) or not-so-good-administrator (very pious muslim)? It is totally hypothetical but this is a scenario. That’s why I believe separating religion from politics is a very good thing. Now we cannot have an exceptionally talented (lets say) minority representative as head of state because he should be a muslim.
Some people might argue that even USA would not allow a Muslim President (just as having an African American president is difficult) so why should Pakistan do that? Correct. But the Constitution of USA does not bar the minorities from taking the charge of President. Its not that "you have to have a minority head of state" as its often difficult (minorities are by definition minorities) but at least there should be no bar constitutionally. Every citizen of a country should have this right.