Here’s the argument that President Obama’s transfer of the U.S. Census operation from the Secretary of Commerce to the political wings of the White House is unconstitutional:
The Secretary of Commerce is the only authority the law recognizes. Since as commenter Laird points out, the Constitution did not place the census function in Article II – the Executive branch but in Article I – the Legislative branch, it is not at all within the President’s reach unless the legislature places it there.
I think that interpretation is supported by phrasing such as this taken from Subchapter 1 section 9 “No department, bureau, agency, officer, or employee of the Government, except the Secretary in carrying out the purposes of this title, shall …”
The Secretary of Commerce does not even report his findings to the President, but rather is instructed to ‘publish’ them. It looks quite clear to me that any incursion by the White House after those two Senate approved appointments is clearly against the law.