Congress has amended section 7441 of the Internal Revenue Code by adding this sentence at the end of that section:
The Tax Court is not an agency of, and shall be independent of, the executive branch of the Government.
--from section 441 of the Protecting Americans from Tax Hikes Act of 2015, Division Q of the Consolidated Appropriations Act, 2016 (H.R. 2029), signed into law by the President on December 18, 2015.
However, section 7443(f) of the Code still provides that a Tax Court judge may be removed by the President "for inefficiency, neglect of duty, or malfeasance in office". So, we may yet see more litigation about the status of the Tax Court.