Are there legitimate grounds for denying people or groups of people admission to the united states

Yes there immigration laws are to deny people or groups of people admission to the United States.

Explanation:

Right to enter into foreign country has been governed by immigration laws pertain to every country. America has a long history of immigration problems from settlers.

So to protect the interest of Native American citizens the US congress has enacted the immigration laws in which it states that right to entry in America is wrested in the hands of presiding immigration officer who will scrutinize the application and decide upon the stay in America.

They have classified many clauses for individual who has to fulfill those requirements before seeking immigration.