Does Congress have the authority to grant citizenship to an individual?

Question

The US House Committee on Appropriations just passed a resolution to grant citizenship to Charlie Gard, a British infant. Of course, the resolution is only part of a much larger bill that would need to be passed into law by Congress/the President.

However, recently there has been a lot of noise from the executive branch of the US Government proclaiming that it has power over immigration granted by the US Constitution, with regard to the various immigration bans the White House has attempted to enact.

Considering this, and understanding that immigration policies in a broad sense probably came from Congress in some form (as there is a lot of existing 'immigration law' on the books), does Congress have the authority to grant citizenship to an individual? Can Congress pass a law that applies to a single, specific individual (rather than an office or position held by an individual, such as the Office of the President of the United States)? Is there any precedent for either of these things?

Answer 1

A law which punishes a specific person – a "bill of attainder" – is unconstitutional. Private laws, which benefit an individual, are legal. An example is Private Law 112-1, which says

Notwithstanding any other provision of law, for the purposes of the Immigration and Nationality Act (8 U.S.C. 1101 et seq.), Sopuruchi Chukwueke shall be deemed to have been lawfully admitted to, and remained in, the United States, and shall be eligible for adjustment of status to that of an alien lawfully admitted for permanent residence under section 245 of the Immigration and Nationality Act (8 U.S.C. 1255) upon filing an application for such adjustment of status.

Nothing prevents such a bill from being made law, where the benefit is a grant of citizenship. Of course, it has to be signed by the president, or else congress must override his veto.